tag:theconversation.com,2011:/us/topics/chlorophyll-12835/articlesChlorophyll – The Conversation2024-03-11T12:25:42Ztag:theconversation.com,2011:article/2229722024-03-11T12:25:42Z2024-03-11T12:25:42ZWhy do trees need sunlight? An environmental scientist explains photosynthesis<figure><img src="https://images.theconversation.com/files/578432/original/file-20240227-20-s7p24d.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2048%2C1364&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The reason trees need sunlight is the same reason their leaves are green.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/scottb211/10108377914/"> Scottb211/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
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<p><strong>Why do trees need sunlight? – Tillman, age 9, Asheville, North Carolina</strong></p>
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<p>Trees need sunlight for the same reason you need food. The energy from the Sun’s rays is a crucial ingredient in how plants make their own food that helps them power all their cells. Since trees don’t harvest or hunt food, they have to produce their own. The way they make their food is a unique and important chemical process called photosynthesis.</p>
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<a href="https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="honey-comb pattern of rings each containing many small green spheres" src="https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=406&fit=crop&dpr=1 600w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=406&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=406&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=510&fit=crop&dpr=1 754w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=510&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/574698/original/file-20240209-30-3fr5f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=510&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Chlorophyll is what makes leaves green.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Plagiomnium_affine_laminazellen.jpeg">Kristian Peters-Fabelfroh/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<h2>What is photosynthesis?</h2>
<p>The cells in plants and all other living things have microscopic components called <a href="https://www.genome.gov/genetics-glossary/Organelle">organelles</a>. One type of organelle in plant cells is the chloroplast, and it contains the <a href="https://www.kidzone.ws/science/lessons/pigments.html">pigment</a> chlorophyll, which is what makes leaves green. When chlorophyll receives sunlight, it starts the <a href="https://education.nationalgeographic.org/resource/photosynthesis">photosynthesis</a> reaction.</p>
<p>The name photosynthesis comes from the ancient Greek words “photo,” which means light, and “synthesis,” which means to make. During this food-making process, plants take carbon dioxide from the air and water from the ground, and with the energy from sunlight, make glucose. Glucose is a very simple type of sugar. Because it is a simple compound, it is simple to make.</p>
<p>Most of the time, photosynthesis occurs in leaves, and leaves take in sunlight to make food. There are some special plants, though, that actually absorb sunlight on their stems. Some of these include cactuses like the balloon-shaped <a href="https://www.gardenia.net/plant/echinocactus-grusonii-golden-barrel-cactus">golden barrel cactus</a>, the spiky <a href="https://huntington.org/educators/learning-resources/spotlight/cylindropuntia-munzii">Munz’s Cholla</a> and the paddle-shaped <a href="https://huntington.org/educators/learning-resources/spotlight/opuntia-ficus-indica">prickly pear</a>. Some plants even have roots that can photosynthesize, like the rare palm <em><a href="https://huntington.org/educators/learning-resources/spotlight/cryosophila-albida">Cryosophila albida</a></em>.</p>
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<a href="https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A graphic diagram of a plant showing sun, soil, roots, leaves and a flower" src="https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=601&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=601&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=601&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=755&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=755&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579708/original/file-20240304-28-wxa438.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=755&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Sunlight gives plants the energy to turn water and carbon dioxide into carbohydrates – the food their cells need to live and grow.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Photosynthesis_en.svg">At09kg/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<h2>Photosynthesis is billions of years old</h2>
<p>Photosynthesis evolved more than <a href="https://doi.org/10.1104%2Fpp.110.161687">3.5 billion years ago</a>. Initially, only single-celled organisms, kind of like today’s algae, could make sugar this way. Oxygen is a waste product from the photosynthesis process, and over time, these single-celled organisms released enough oxygen to change the Earth’s atmosphere. Ultimately, we and all other animals needed this to happen to be able to live and breathe. </p>
<p>Over time, aquatic plants developed, and gradually plants <a href="https://doi.org/10.1126/science.aat3642">moved to land</a> around 500 million years ago to better access their most vital resource: sunlight. Plants eventually got taller by around <a href="https://doi.org/10.1126/science.aar2986">350 million years ago</a>. This is when the first tree evolved, which grew up to 150 feet tall. These trees looked like the evergreen trees we see today – sort of like pines, firs and spruce. And about 125 million years ago, trees that looked like the maples, oaks and beech trees we see today shared the landscape when <a href="https://new.nsf.gov/news/dinosaur-age-fossils-provide-new-insights-origin">dinosaurs ruled the Earth</a>.</p>
<h2>Not just good for plants</h2>
<p>The Sun provides energy for the Earth. However, we humans are not capable of taking in the sun directly and using it to power our bodies. So how do we make use of the Sun’s energy? Plants do it for us.</p>
<p>Plants take in that energy and make food for us and other animals to eat and oxygen for us to breathe. We wouldn’t exist without plants and photosynthesis.</p>
<p>Like the ancient tiny single-celled organisms from 3.5 billion years ago, some microorganisms today use photosynthesis. Specifically, the algae that you might see living on top of lakes and the ocean do. Chlorophyll is why algae is green. </p>
<p>There are <a href="https://news.asu.edu/20191114-asu-study-shows-some-aquatic-plants-depend-landscape-photosynthesis">aquatic plants</a> that use sunlight to grow. They typically make use of less sunlight because sunlight does not travel well through water.</p>
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<span class="caption">Some plants can do photosynthesis underwater, where there is less sunlight.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/chesbayprogram/32446887586/">Chesapeake Bay Program/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
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<p>In addition, there are a very few animals that can photosynthesize. The <a href="https://doi.org/10.1038/nature.2012.11214">pea aphid</a> uses pigment to harvest sunlight to make energy. The <a href="https://phys.org/news/2011-01-physicists-outer-shell-hornet-harvest.html">Oriental hornet</a> uses a pigment in its exoskeleton to make energy from sunlight. The <a href="https://www.nationalgeographic.com/animals/article/solar-powered-photosynthetic-sea-slugs-in-decline-news">emerald-green sea slug</a> eats algae and then incorporates chlorophyll from the algae into its body to photosynthesize. Because of this strategy, the sea slug can go nine months without eating. </p>
<p>So the answer to this question – why do trees need sunlight – is to make their food. And thanks to trees and other plants turning sunlight into their food, most of the rest of the living things on Earth get to eat, too!</p>
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<p class="fine-print"><em><span>Rebekah Stein does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Trees – and all plants – harvest sunlight to gain the energy they need to live and grow.Rebekah Stein, Assistant Professor of Environmental Science, Quinnipiac UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2109972023-10-23T12:25:38Z2023-10-23T12:25:38ZA layered lake is a little like Earth’s early oceans − and lets researchers explore how oxygen built up in our atmosphere billions of years ago<figure><img src="https://images.theconversation.com/files/542374/original/file-20230811-17-9wl0g5.jpeg?ixlib=rb-1.1.0&rect=0%2C12%2C4031%2C2692&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Researchers sample water from various layers to analyze back in the lab.</span> <span class="attribution"><span class="source">Elizabeth Swanner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Little Deming Lake doesn’t get much notice from visitors to <a href="https://www.dnr.state.mn.us/state_parks/park.html?id=spk00181#homepage">Itasca State Park</a> in Minnesota. There’s better boating on nearby Lake Itasca, the headwaters of the Mississippi River. My colleagues and I need to maneuver hundreds of pounds of equipment down a hidden path made narrow by late-summer poison ivy to launch our rowboats.</p>
<p>But modest Deming Lake offers more than meets the eye for <a href="https://scholar.google.com/citations?user=QopCtZ4AAAAJ&hl=en&oi=ao">me, a geochemist</a> interested in how oxygen built up in the atmosphere 2.4 billion years ago. The absence of oxygen in the deep layers of Deming Lake is something this small body of water has in common with early Earth’s oceans.</p>
<p>On each of our several expeditions here each year, we row our boats out into the deepest part of the lake – over 60 feet (18 meters), despite the lake’s surface area being only 13 acres. We drop an anchor and connect our boats in a flotilla, readying ourselves for the work ahead.</p>
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<span class="caption">Researchers’ boats on Deming Lake.</span>
<span class="attribution"><span class="source">Elizabeth Swanner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>Deming Lake is <a href="https://www.worldatlas.com/articles/what-is-a-meromictic-lake.html">meromictic</a>, a term from Greek that means only partially mixing. In most lakes, at least once a year, the water at the top sinks while the water at the bottom rises because of wind and seasonal temperature changes that affect water’s density. But the <a href="https://eartharxiv.org/repository/view/4827/">deepest waters of Deming Lake never reach the surface</a>. This prevents oxygen in its top layer of water from ever mixing into its deep layer.</p>
<p>Less than 1% of lakes are meromictic, and most that are have dense, salty bottom waters. Deming Lake’s deep waters are not very salty, but of the salts in its bottom waters, <a href="https://doi.org/10.1016/j.earscirev.2020.103430">iron is one of the most abundant</a>. This makes Deming Lake one of the rarest <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/meromictic-lake">types of meromictic lakes</a>.</p>
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<span class="caption">Postdoc researcher Sajjad Akam collects a water sample for chemical analysis back in the lab.</span>
<span class="attribution"><span class="source">Elizabeth Swanner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>The lake surface is calm, and the still air is glorious on this cool, cloudless August morning. We lower a 2-foot-long water pump zip-tied to a cable attached to four sensors. The sensors measure the temperature, amount of oxygen, pH and amount of chlorophyll in the water at each layer we encounter. We pump water from the most intriguing layers up to the boat and fill a myriad of bottles and tubes, each destined for a different chemical or biological analysis.</p>
<p>My colleagues and I have homed in on Deming Lake to explore questions about how microbial life adapted to and changed the environmental conditions on early Earth. Our planet was inhabited <a href="https://theconversation.com/were-viruses-around-on-earth-before-living-cells-emerged-a-microbiologist-explains-197880">only by microbes</a> for most of its history. The atmosphere and the oceans’ depths didn’t have much oxygen, but they did have a lot of iron, just like Deming Lake does. By investigating what Deming Lake’s microbes are doing, we can better understand how billions of years ago they helped to transform the Earth’s atmosphere and oceans into what they’re like now.</p>
<h2>Layer by layer, into the lake</h2>
<p>Two and a half billion years ago, ocean waters had enough iron to form today’s globally distributed <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/banded-iron-formation">rusty iron deposits called</a> <a href="https://www.amnh.org/exhibitions/permanent/planet-earth/how-has-the-earth-evolved/banded-iron-formation">banded iron formations</a> that supply iron for the modern global steel industry. Nowadays, oceans have only <a href="https://youtu.be/EpzEv0H4lvg">trace amounts of iron</a> but abundant oxygen. In most waters, iron and oxygen are antithetical. Rapid <a href="https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(Boundless)/05%3A_Microbial_Metabolism/5.10%3A_Chemolithotrophy/5.10D%3A__Iron_Oxidation">chemical and biological reactions between iron and oxygen</a> mean you can’t have much of one while the other is present.</p>
<p>The rise of oxygen in the early atmosphere and ocean was due to <a href="https://ucmp.berkeley.edu/bacteria/cyanointro.html">cyanobacteria</a>. These single-celled organisms <a href="https://asm.org/Articles/2022/February/The-Great-Oxidation-Event-How-Cyanobacteria-Change">emerged at least 2.5 billion years ago</a>. But it took roughly 2 billion years for the oxygen they produce via photosynthesis to build up to <a href="https://askanearthspacescientist.asu.edu/oxygen-animal-evolution">levels that allowed for the first animals</a> to appear on Earth.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="water concentrated on a filter looks pale green" src="https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=471&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=471&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=471&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=592&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=592&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554308/original/file-20231017-27-m0c4vb.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=592&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Chlorophyll colors water from the lake slightly green.</span>
<span class="attribution"><span class="source">Elizabeth Swanner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>At Deming Lake, my colleagues and I pay special attention to the water layer where the chlorophyll readings jump. <a href="https://www.britannica.com/science/chlorophyll">Chlorophyll is the pigment</a> that makes plants green. It harnesses sunlight energy to turn water and carbon dioxide into oxygen and sugars. Nearly 20 feet (6 meters) below Deming’s surface, the chlorophyll is in cyanobacteria and photosynthetic algae, not plants. </p>
<p>But the curious thing about this layer is that we don’t detect oxygen, despite the abundance of these oxygen-producing organisms. This is the depth where iron concentrations start to climb to the high levels present at the lake’s bottom.</p>
<p>This high-chlorophyll, high-iron and low-oxygen layer is of special interest to us because it might help us understand where cyanobacteria lived in the ancient ocean, how well they were growing and how much oxygen they produced. </p>
<p>We suspect the reason cyanobacteria gather at this depth in Deming Lake is that there is more iron there than at the top of the lake. Just like <a href="https://theconversation.com/blood-in-your-veins-is-not-blue-heres-why-its-always-red-97064">humans need iron for red blood cells</a>, cyanobacteria need lots of iron to help catalyze the reactions of photosynthesis.</p>
<p>A likely reason we can’t measure any oxygen in this layer is that in addition to cyanobacteria, there are a lot of other bacteria here. After a good long life of a few days, the cyanobacteria die, and the other bacteria feed on their remains. These bacteria rapidly use up any oxygen produced by still photosynthesizing cyanobacteria the way a fire does as it burns through wood.</p>
<p>We know there are lots of bacteria here based on how cloudy the water is, and we see them when we inspect a drop of this water under a microscope. But we need another way to measure photosynthesis besides measuring oxygen levels. </p>
<h2>Long-running lakeside laboratory</h2>
<p>The other important function of photosynthesis is converting carbon dioxide into sugars, which eventually are used to make more cells. We need a way to track whether new sugars are being made, and if they are, whether it’s by photosynthetic cyanobacteria. So we fill glass bottles with samples of water from this lake layer and seal them tight with rubber stoppers.</p>
<p>We drive the 3 miles back to the <a href="https://cbs.umn.edu/itasca">Itasca Biological Station and Laboratories</a> where we will set up our experiments. The station opened in 1909 and is home base for us this week, providing comfy cabins, warm meals and this laboratory space.</p>
<p>In the lab, we inject our glass bottle with carbon dioxide that carries an <a href="https://www.britannica.com/science/isotopic-tracer">isotopic tracer</a>. If cyanobacteria grow, their cells will incorporate this isotopic marker. </p>
<p>We had a little help to formulate our questions and experiments. University of Minnesota students attending summer field courses collected decades worth of data in Itasca State Park. A diligent university librarian digitized <a href="https://cbs.umn.edu/itasca/research/student-research-papers">thousands of those students’ final papers</a>.</p>
<p>My students and I pored over the papers concerning Deming Lake, many of which tried to determine whether the cyanobacteria in the chlorophyll-rich layer are doing photosynthesis. While most indicated yes, those students were measuring only oxygen and got ambiguous results. Our use of the isotopic tracer is trickier to implement but will give clearer results.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="woman holds a clear plastic bag aloft, she and man are seated in boat" src="https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554313/original/file-20231017-17-p7jytu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Graduate students Michelle Chamberlain and Zackry Stevenson about to sink the bottles for incubation in Deming Lake.</span>
<span class="attribution"><span class="source">Elizabeth Swanner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>That afternoon, we’re back on the lake. We toss an anchor; attached to its rope is a clear plastic bag holding the sealed bottles of lake water now amended with the isotopic tracer. They’ll spend the night in the chlorophyll-rich layer, and we’ll retrieve them after 24 hours. Any longer than that and the isotopic label might end up in the bacteria that eat the dying cyanobacteria instead of the cyanobacteria themselves. We tie off the rope to a floating buoy and head back to the station’s dining hall for our evening meal.</p>
<h2>Iron, chlorophyll, oxygen</h2>
<p>The next morning, as we wait for the bottles to finish their incubation, we collect water from the different layers of the lake and add some chemicals that kill the cells but preserve their bodies. We’ll look at these samples under the microscope to figure out how many cyanobacteria are in the water, and we’ll measure how much iron is inside the cyanobacteria. </p>
<p>That’s easier said than done, because we have to first separate all the “needles” (cyanobacteria) from the “hay” (other cells) and then clean any iron off the outside of the cyanobacteria. Back at Iowa State University, we’ll shoot the individual cells one by one into a flame that incinerates them, which liberates all the iron they contain so we can measure it.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="rowboat with one woman in it on a lake with woodsy shoreline" src="https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554323/original/file-20231017-27-p7jytu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Biogeochemist Katy Sparrow rows a research vessel to shore.</span>
<span class="attribution"><span class="source">Elizabeth Swanner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Our scientific hunch, or <a href="https://www.britannica.com/science/scientific-hypothesis">hypothesis</a>, is that the cyanobacteria that live in the chlorophyll- and iron-rich layer will contain more iron than cyanobacteria that live in the top lake layer. If they do, it will help us establish that greater access to iron is a motive for living in that deeper and dimmer layer.</p>
<p>These experiments won’t tell the whole story of why it took so long for Earth to build up oxygen, but they will help us to understand a piece of it – where oxygen might have been produced and why, and what happened to oxygen in that environment.</p>
<p>Deming Lake is quickly becoming its own attraction for those with a curiosity about what goes on beneath its tranquil surface – and what that might be able to tell us about how new forms of life took hold long ago on Earth.</p><img src="https://counter.theconversation.com/content/210997/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Elizabeth Swanner receives funding from the U.S. National Science Foundation and the National Aeronautics and Space Administration. </span></em></p>An unusual lake with distinct layers of low-oxygen and high-iron water lets researchers investigate conditions like those in the early Earth’s oceans.Elizabeth Swanner, Associate Professor of Geology, Iowa State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1942512022-11-30T02:42:03Z2022-11-30T02:42:03ZChlorophyll water can’t clear your skin or detox your liver. But this TikTok trend got one thing right<figure><img src="https://images.theconversation.com/files/494378/original/file-20221109-12-y2eyjf.jpg?ixlib=rb-1.1.0&rect=1%2C110%2C772%2C555&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/close-chlorophyll-water-2047018778">Shutterstock</a></span></figcaption></figure><p>If you follow health trends online, you might have heard about “chlorophyll water”. Claims range from <a href="https://www.allure.com/story/tiktok-drinking-liquid-chlorophyll-skin-care-benefits">clearing your skin</a>, stopping <a href="https://www.healthline.com/health/chlorophyll-bad-breath">body odour</a>, increasing <a href="https://chlorophyllwater.com">energy and oxygen</a>, to <a href="https://www.verywellfit.com/health-benefits-liquid-chlorophyll-4686266">detoxing your liver</a> and <a href="https://www.healthline.com/health/liquid-chlorophyll-benefits-risks">preventing cancer</a>. </p>
<p>Chlorophyll water is sold as a liquid concentrate or already mixed with water. Numerous TikTok videos claim its health benefits.</p>
<p><iframe id="tc-infographic-792" class="tc-infographic" height="400px" src="https://cdn.theconversation.com/infographics/792/2a5a434e96e20c6436cb180cbfe25b2f7b8a3dbc/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Then there are celebrity endorsements for chlorophyll water, including from <a href="https://chlorophyllwater.medium.com/the-benefits-of-drinking-chlorophyll-water-by-kourtney-kardashian-poosh-50a3536cb123">Kourtney Kardashian</a> on her <a href="https://poosh.com/chlorophyll-water-benefits/">lifestyle channel</a>.</p>
<p>So, what is chlorophyll water? And is it really a healthy choice?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/lemon-water-wont-detox-or-energise-you-but-it-may-affect-your-body-in-other-ways-180035">Lemon water won't detox or energise you. But it may affect your body in other ways</a>
</strong>
</em>
</p>
<hr>
<h2>Remind me again, what’s chlorophyll?</h2>
<p>What you might remember about chlorophyll from high-school science might sound pretty healthy. </p>
<p><a href="http://www.chm.bris.ac.uk/motm/chlorophyll/chlorophyll_h.htm">Chlorophyll</a> is the pigment that gives plants (and some algae and bacteria) their green colour. It is vital for <a href="https://education.nationalgeographic.org/resource/photosynthesis">photosynthesis</a>, the process that uses sunlight to produce oxygen and chemical energy stored in the sugar glucose.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Light shining through green palm fronds" src="https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Yes, you do remember correctly. Plants need chlorophyll to generate oxygen and energy.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/sun-shining-through-radiating-green-leaf-391408468">Shutterstock</a></span>
</figcaption>
</figure>
<p>At the heart of most chlorophyll is <a href="https://ods.od.nih.gov/factsheets/Magnesium-Consumer">magnesium</a> – an essential nutrient for humans – needed for healthy nerves and muscles, regulating blood sugar and blood pressure, and building bones, proteins and DNA. </p>
<p>The chemical structure of chlorophyll looks a bit like <a href="https://pubmed.ncbi.nlm.nih.gov/24670123/">protoheme</a>. That’s the red part of our haemoglobin, the part of red blood cells that carries oxygen in our blood.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-are-leaves-green-86160">Curious Kids: Why are leaves green?</a>
</strong>
</em>
</p>
<hr>
<h2>So, what is chlorophyll water then?</h2>
<p>Water plus pigments that keep plants healthy, and that contain nutrients humans need, sounds great. Unfortunately, it’s not so simple. </p>
<p>First, chlorophyll doesn’t dissolve in water. So, what you get in these products isn’t “natural from plants”. It’s the molecule <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/chlorophyllin#:%7E:text=Chlorophyllin%20is%20a%20semisynthetic%20chlorophyll,and%20have%20good%20water%20solubility.">chlorophyllin</a>. Chlorophyllin is made from chlorophyll by a process called <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5039533">saponification</a>.</p>
<p>Essentially, this involves reacting it with sodium hydroxide and making a smaller molecule that is water-friendly. Then, to help it stay bright green, another reaction replaces the magnesium with copper, <a href="https://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/chlorophyll-metallo-chlorophyll-derivatives">which is much more stable</a>. </p>
<p>A more accurate name for these products would be “sodium copper chlorophyllin water”. But that’s not quite so marketable.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Woman dropping chlorophyll extract into glass of water" src="https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=395&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=395&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=395&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=497&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=497&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=497&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Is that ‘chlorophyll water’ or ‘sodium copper chlorophyllin water’? One sounds easier to swallow.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/woman-dripping-chlorophyll-supplement-into-glass-2130227768">Shutterstock</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/does-tiktoks-chia-lemon-internal-shower-really-beat-constipation-heres-what-science-says-188744">Does TikTok's chia-lemon 'internal shower' really beat constipation? Here's what science says</a>
</strong>
</em>
</p>
<hr>
<h2>But is it healthy?</h2>
<p>Just because it’s been converted from its natural form, doesn’t make it automatically unhealthy. So how do the health claims stack up?</p>
<p>There is lots of evidence about diets high in chlorophyll being healthy. But, since evidence is mostly diets <a href="https://www.sciencedirect.com/science/article/pii/B9780128008720000184">high in green plant foods</a>, this can’t be directly translated into water containing a processed derivative of one little part of green plants. </p>
<p>There is <a href="https://pubmed.ncbi.nlm.nih.gov/24670123/">some evidence</a> that comes from the extracted, processed form (chlorophyllin). But that’s mostly from animal or lab studies. These involve very high concentrations that would need you to drink dramatic levels of chlorophyll water to match the doses, or to inject it deep into your cells. To be clear, please don’t do either.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/science-or-snake-oil-can-a-detox-actually-cleanse-your-liver-56344">Science or Snake Oil: can a detox actually cleanse your liver?</a>
</strong>
</em>
</p>
<hr>
<p>There are also some (mostly very small) studies about its impacts on <a href="https://pubmed.ncbi.nlm.nih.gov/25844615/">skin</a> and its use as a <a href="https://jamanetwork.com/journals/jama/article-abstract/287788">deodorant</a>, but most of these are about applying chlorophylls and chlorophyllins directly to the skin. You don’t need to be a scientist to know that’s not the same as drinking it in water.</p>
<p>How about boosting your energy and oxygen? It might make sense on simple logic because this is what it does in plants, and the pigment’s similarities to haemoglobin. </p>
<p>But there is no data to support these claims. We do have a small pilot <a href="https://www.semanticscholar.org/paper/A-pilot-study-on-wheat-grass-juice-for-its-and-on-Chauhan/73f2bb7c0b1129b5da66ca284eb2294d956fa9d2?p2df">study</a> of wheatgrass and the blood disorder thalassemia. But wheatgrass is much more complex than just chlorophyll and what helps someone with a disorder doesn’t necessarily make the rest of us healthier.</p>
<h2>So why do so many people say they feel better?</h2>
<p>First, who’s making the testimonials on social media? Do you trust them? Could it be <a href="https://digitalcommons.uri.edu/tmd_major_papers/2/">advertising</a> rather than someone’s own personal experience?</p>
<p>Second, it could be the “<a href="https://www.jneurosci.org/content/31/45/16117.short">placebo effect</a>”, where just taking something that feels like a treatment makes you feel better. </p>
<p>But most importantly, the main ingredient in chlorophyll water is water.</p>
<p>This is definitely <a href="https://www.eatforhealth.gov.au/nutrient-reference-values/nutrients/water">an essential nutrient</a>, and definitely something we want to encourage people to drink more of. </p>
<p>By turning to chlorophyll water, people may be simply increasing their water intake, and decreasing their intake of sugary drinks or alcohol. <a href="https://www.mdpi.com/2072-6643/11/1/70">Improving hydration</a> alone could explain their reports. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-do-i-wake-up-thirsty-183731">Why do I wake up thirsty?</a>
</strong>
</em>
</p>
<hr>
<h2>Are there any risks?</h2>
<p>Excessive consumption (multiple doses a day) <a href="https://www.tandfonline.com/doi/full/10.3109/19390211.2013.859853">could cause some side effects</a> such as nausea, stomach upsets, discolouring your poo and staining your teeth.</p>
<p>Like all supplements, there is a risk chlorophyll water may interact with <a href="https://www.webmd.com/vitamins-and-supplements/chlorophyll-uses-and-risks">medications</a>. And there haven’t been big safety studies in at-risk groups, such as people who are pregnant or breastfeeding. So caution is advised.</p>
<p><iframe id="tc-infographic-793" class="tc-infographic" height="400px" src="https://cdn.theconversation.com/infographics/793/82c1dfb245279ba2e4f858eac103dad66412fdbc/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>But, stop and think about the potential indirect downsides of drinking chlorophyll water. It’s expensive. Chlorophyll concentrate, which you’d dilute with water, costs about <a href="https://www.chemistwarehouse.com.au/buy/58504/swisse-chlorophyll-spearmint-500ml?gclid=Cj0KCQiA1NebBhDDARIsAANiDD0o1EzK7XgJq3xR0yfswtGg_Uc4U3zJ2Ec1CkEEFe8KXVcFbjmtBZIaAmd_EALw_wcB&gclsrc=aw.ds">A$16</a> for a 500mL bottle. So it could be an expensive way of increasing your water intake if you think you’re not drinking enough, given tap water is safe and cheap. </p>
<p>Even if there are any benefits, you could get these benefits from eating actual plant foods. So the money and time you spend buying chlorophyll water could be taking money and time away from other food and drink choices that could have much bigger health benefits. </p>
<h2>The bottom line</h2>
<p>If you like it, can afford it, and don’t have any medication risks, the choice is yours. </p>
<p>You could also try other ways to increase your chlorophyll intake, such as eating more green veggies. You could add cheaper things to water to make it appealing, such as mint, fruit or teas. </p>
<p>These options could be cheaper and have even better health impacts, but probably won’t get as many views on TikTok. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/wellness-is-not-womens-friend-its-a-distraction-from-what-really-ails-us-177446">Wellness is not women's friend. It’s a distraction from what really ails us</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/194251/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Emma Beckett has received funding for research or consulting from Mars Foods, Nutrition Research Australia, NHMRC, ARC, AMP Foundation, Kellogg, and the University of Newcastle. She is a member of committees/working groups related to nutrition or the Australian Academy of Science, the National Health and Medical Research Council and the Nutrition Society of Australia. </span></em></p>Health claims for chlorophyll water are all over TikTok. We looked at the evidence to see what stacked up.Emma Beckett, Senior Lecturer (Food Science and Human Nutrition), School of Environmental and Life Sciences, University of NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1811632022-04-14T05:30:09Z2022-04-14T05:30:09ZMulti-coloured plants are suddenly a home decor ‘must-have’. Here’s how to keep them alive<figure><img src="https://images.theconversation.com/files/457621/original/file-20220412-46278-pqir8z.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5065%2C3785&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Fads and fashion have always influenced the plants we keep. And so it is with variegated plants, which have become <a href="https://thatplantylife.com/affordable-and-gorgeous-variegated-houseplants/">very popular</a> with indoor plant enthusiasts these days.</p>
<p>Variegated plants possess multiple colours – typically on their leaves, but in some cases on stems, flowers and fruit. Their patterns include stripes, dots, edges and patches. They’re usually green with either white or yellow, but can also feature red, pink, silver and other colours.</p>
<p>Variegated plants can divide opinion. I recall a great aunt telling me many years ago of her great fondness for the variegated Aspidistra elatior growing her garden. But I’ve also heard gardeners and garden designers dismiss variegated foliage because it didn’t fit with their design or colour themes.</p>
<p>Now, it seems indoor variegated plants are considered a “<a href="https://www.apartmenttherapy.com/variegated-plant-care-tips-36878935">must-have</a>” home decor accessory. But before you rush out and buy one, make sure you know how to keep it happy.</p>
<figure class="align-center ">
<img alt="woman puts handful of dirt into plant pot" src="https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.jpg?ixlib=rb-1.1.0&rect=14%2C22%2C4889%2C3235&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457618/original/file-20220412-9671-rkr9nz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Variegated plants come in an array of colours and patterns.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Understanding variegated plants</h2>
<p>Most plant species are entirely green but occasionally a variegated individual arises. Some catch the eye of a dedicated plant collector or nursery worker and become a popular variety.</p>
<p>Plant variegation can occur for several reasons.</p>
<p>In some plants, such as the flowers of tulips, it’s due to a <a href="https://www.britannica.com/story/tulip-mania-how-a-plant-virus-fueled-a-speculative-frenzy">viral infection</a>. The resulting streaks of different colours may be cursed or valued depending on the aesthetic effect.</p>
<p>Others plants, such as those in the genus <a href="https://www.rbgsyd.nsw.gov.au/Stories/2019/Coleus-back-in-the-name-game">coleus</a>, are naturally patterned. Groups of cells produce different colour combinations, causing leaves to grow with attractive markings.</p>
<p>Plant variegations can also arise from genetic mutation.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-are-leaves-green-86160">Curious Kids: Why are leaves green?</a>
</strong>
</em>
</p>
<hr>
<p>When growing variegated plants, it’s important to understand how the various colours affect the way it functions.</p>
<p>The green part of plants contains chlorophyll, a pigment essential for photosynthesis. (Photosynthesis, of course, is the process by which the leaves convert sunlight into oxygen and carbohydrate that provides energy for plants to grow.) </p>
<p>In variegated plants, white parts of leaves do not contain chlorophyll and so do not photosynthesise. </p>
<p>Yellow parts of leaves can help send energy to the chlorophyll, but can’t perform photosynthesis on their own. The same goes for some red, orange and pink patches of tissue.</p>
<p>But all cells in the leaf – green or not – use the plant’s energy. That means variegated plants are less efficient energy producers than their all-green counterparts, which causes them to grow more slowly.</p>
<p>Some plants have mutated into <a href="https://www.chicagobotanic.org/blog/how_to/science_activity_albino_plants">albinos</a> containing no chlorophyll. These normally die within a few days or weeks of germination.</p>
<figure class="align-center ">
<img alt="two indoor variegated plants in pots" src="https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457623/original/file-20220412-36930-x4khyj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Yellow parts of leaves do not photosynthesise.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Caring for your plant indoors</h2>
<p>It’s no coincidence many popular indoor plants – such as coleus, philodendrons, monsteras, dracaenas and calatheas – are variegated. Because they’re usually far less vigorous than all-green versions of the species, they won’t be pushing against the ceiling within weeks. </p>
<p>The decorative colour and pattern of a variegated indoor plant is an added bonus.</p>
<p>Variegated plants can take longer than others to reach a size considered appropriate for sale at a nursery, so may be comparatively more expensive. But there are ways to protect your variegated investment.</p>
<p>First, watch out for “reversion”. This can occur when a variegated plant sends up an all-green shoot. The shoot will grow fast compared to the variegated parts and can eventually take over, causing the whole plant to revert to green. </p>
<p>To avoid this, vigilantly remove any green shoots before they get big.</p>
<p>You don’t want variegated plants quickly outgrowing their space, but remember they’re low on chlorophyll and so need good light.</p>
<p>And like any indoor plant, ensure its leaves are kept free of fine dust and you don’t give it too much, or too little, water.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-apartment-dwellers-need-indoor-plants-80196">Why apartment dwellers need indoor plants</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="plants on sun-drenched windowsill" src="https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457625/original/file-20220412-26-9divrh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Indoor variegated plants need good light to make up for the lack of chlorophyll.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Variegated plants in the garden</h2>
<p>The popularity of indoor variegated plants will almost certainly lead to greater use outdoors.</p>
<p>Their slow-growing nature means outdoor variegated plants are usually much less likely to be “weedy” and spread where they’re not wanted. </p>
<p>This can be an advantage if you’ve avoided planting a species because it will take over the garden. The variegated versions of <a href="https://www.plantmark.com.au/pittosporum-eugenioides-variegata">pittosporum</a>, ficus and <a href="https://www.rhs.org.uk/plants/57250/nerium-oleander-variegatum-(v)/details">nerium oleander</a>, for example, are far less intent on global domination than their all-green counterparts.</p>
<p>When planting a variegated plant outdoors, watch that it doesn’t become shaded by other quicker-growing plants. Many variegated plants already struggle to photosynthesise sufficiently. A bit of extra shade can damage or even kill them.</p>
<p>So ensure they get enough light – and every so often give them a hand by trimming back nearby plants.</p>
<figure class="align-center ">
<img alt="green and purple plants in garden" src="https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457629/original/file-20220412-23-r12327.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ensure variegated plants are not over-shaded.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Growing with flying colours</h2>
<p>Variegated plants are having their moment in the sun. But their interesting biology is always in fashion!</p>
<p>These plants can brighten up your indoor space and provide attractive colour and pattern in the garden.</p>
<p>By learning about how variegated plants function and considering their special requirements, you can enjoy them for years to come.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/trees-get-sunburnt-too-but-there-are-easy-ways-to-protect-them-from-tree-sunscreen-to-hydration-172953">Trees get sunburnt too – but there are easy ways to protect them, from tree 'sunscreen' to hydration</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/181163/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gregory Moore does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Variegated plants can be more expensive than their all-green counterparts. But there are ways to protect your investment.Gregory Moore, Doctor of Botany, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1237442019-10-21T12:17:22Z2019-10-21T12:17:22ZWhy don’t evergreens change color and drop their leaves every fall?<figure><img src="https://images.theconversation.com/files/297827/original/file-20191021-56242-1wgq120.jpg?ixlib=rb-1.1.0&rect=51%2C0%2C3399%2C2291&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What's happening with the trees that stay green?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/beautiful-fall-foliage-golden-yellow-aspen-1503622133?src=Hr3x35_H4DbsNorTrIHA5Q-1-7">BingHao/Shutterstock.com</a></span></figcaption></figure><p>It’s autumn in the Northern Hemisphere – otherwise known as leaf-peeping season. Now is when people head outside to soak up the annual display of orange, red and yellow foliage painted across the landscape.</p>
<p>But mixed among those bright, colorful patches are some trees that stay steadfastly green. Why do evergreen conifers sit out this blazing seasonal spectacle?</p>
<p>Like so many other challenges, the problem of winter can be solved by trees in more than one way.</p>
<p>As temperatures begin to dip, broad-leafed temperate trees – think maples and oaks – withdraw the green chlorophyll from their leaves. That’s the pigment that absorbs sunlight to power photosynthesis. Trees store the hard-won minerals, chiefly nitrogen, they’ve invested in chlorophyll in their wood for reuse in a future growing season. Yellows and oranges and reds are left fleetingly visible before the leaves drop for winter.</p>
<p>Evergreen conifers – cone-bearing trees – retain their foliage year-round and have a different strategy for withstanding winter’s stresses.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/297828/original/file-20191021-56215-2mmbil.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/297828/original/file-20191021-56215-2mmbil.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/297828/original/file-20191021-56215-2mmbil.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/297828/original/file-20191021-56215-2mmbil.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/297828/original/file-20191021-56215-2mmbil.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/297828/original/file-20191021-56215-2mmbil.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/297828/original/file-20191021-56215-2mmbil.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/297828/original/file-20191021-56215-2mmbil.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Green starts to stand out in the fall woods.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/wonderful-autumn-landscape-evergreen-pine-tree-1531872623">Michele Ursi/Shutterstock.com</a></span>
</figcaption>
</figure>
<h2>Return on investment in leaves</h2>
<p>Staying evergreen is not about continuing to conduct photosynthesis throughout the winter. Cold temperatures affect conifers’ metabolism just as they do any other organism’s. In fact, on cold wintry days, evergreen conifers <a href="https://doi.org/10.1641/0006-3568(2004)054%5B0041:PSOOE%5D2.0.CO;2">perform no more photosynthesis</a> than their leafless neighbors.</p>
<p>The best way to understand the benefit of evergreenness is by considering the construction costs of leaves. Needles are really just modified leaves, after all. How do trees balance the energy it takes to grow a leaf with the energy that leaf produces via photosynthesis? In other words, how long do the leaves take to repay their construction costs and offer the tree a return on its investment?</p>
<p>Deciduous trees must recoup their investment in their leafy canopy in only a single growing season. In contrast, evergreen conifers, by hanging onto their needles, grant those needles multiple growing seasons to contribute to their tree’s balance sheets. That’s the real benefit to staying green.</p>
<p>Evergreens’ greater leaf longevity means they can survive in environments that just don’t work for their deciduous cousins. At higher latitudes and elevations, shorter and cooler growing seasons can limit photosynthetic activity. Drought can further interfere with photosynthesis. In these harsher conditions, a year may not be long enough for a leaf to produce enough energy to pay back its growth costs to the tree.</p>
<p>This may explain why evergreen conifers dominate mountaintops and the boreal forests that stretch across high latitudes in Alaska, Canada and Northern Europe. Deciduous broad-leafed trees largely drop out of such habitats – conditions mean they can’t balance their accounts with respect to investments in leaves and leaves’ photosynthetic return in a single season.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/297829/original/file-20191021-56207-5szf6d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/297829/original/file-20191021-56207-5szf6d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/297829/original/file-20191021-56207-5szf6d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/297829/original/file-20191021-56207-5szf6d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/297829/original/file-20191021-56207-5szf6d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/297829/original/file-20191021-56207-5szf6d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/297829/original/file-20191021-56207-5szf6d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/297829/original/file-20191021-56207-5szf6d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">White pine needles need to withstand only one winter.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/white-pine-branch-118531429">Candia Baxter/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>Evergreen needle longevity varies widely and maps onto the degree of growing season stress. Some temperate trees common to southern New England, such as white pine, retain needles for only two growing seasons. Any individual white pine needle overwinters only once, minimally meeting the definition of evergreen.</p>
<p>Some conifers, such as larch, do not achieve even that, instead shedding their entire crown of needles each autumn in a luminously golden display that can be a highlight of the autumn foliage splendor where they are found.</p>
<p>In contrast, bristlecone pines, inhabitants of high elevations in the arid Southwest, hang onto individual needles for almost 50 years. It may take nearly that long for bristlecone pine needles to achieve a photosynthetic return on the investment in their construction, given the growing-season stresses they confront.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/297830/original/file-20191021-56220-nv8teh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/297830/original/file-20191021-56220-nv8teh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/297830/original/file-20191021-56220-nv8teh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=477&fit=crop&dpr=1 600w, https://images.theconversation.com/files/297830/original/file-20191021-56220-nv8teh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=477&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/297830/original/file-20191021-56220-nv8teh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=477&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/297830/original/file-20191021-56220-nv8teh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=599&fit=crop&dpr=1 754w, https://images.theconversation.com/files/297830/original/file-20191021-56220-nv8teh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=599&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/297830/original/file-20191021-56220-nv8teh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=599&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tough bristlecone pine needles last for decades in their harsh habitat.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/bristlecone-pines-oldest-living-things-on-54172333">Darren J. Bradley/Shutterstock.com</a></span>
</figcaption>
</figure>
<h2>Adapting to deal with winter stresses</h2>
<p>Overwintering is profoundly stressful for trees.</p>
<p>Subzero temperatures bring the risk of cellular freezing in evergreen needles – which would be lethal. To prevent freezing, evergreen conifers accumulate high concentrations of <a href="https://doi.org/10.1242/jeb.01730">dissolved substances</a> <a href="https://www.ncbi.nlm.nih.gov/pubmed/15660165">known as cryoprotectants</a> that <a href="https://press.princeton.edu/books/paperback/9780691612638/biochemical-adaptation">lower the freezing point</a> of water in their cells and <a href="https://doi.org/10.1046/j.1365-3040.1998.00309.x">protect key cell structures</a>, while not interfering with metabolism.</p>
<p>Cold, snow and blowing ice, along with the demands of longevity, lead evergreen conifers to invest their energy in the toughness of needles. Conifer needles vary in toughness; for instance, relatively short-lived white pine needles are more delicate. The fibrous materials that make needles more durable further deepen coniferous trees’ investment, extending the period required to achieve a return on needle construction costs.</p>
<p>Heavy loads of snow can result in broken branches, a prevailing risk of evergreenness. Thin, often drooping conifer needles catch less snow than the broad leaves of deciduous trees. Indeed, when deciduous trees lose branches to snowstorms, it is generally during storms on the edges of the snow season – in autumn or spring – not midwinter storms, when the crowns are leafless. If you’ve ever wondered why deciduous trees are taking so long in spring to leaf out, missing out on some excellent growing days as a result, keep in mind that trees don’t want to risk the damage that could result from a freak spring storm.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/297831/original/file-20191021-56194-p4ls9f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/297831/original/file-20191021-56194-p4ls9f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/297831/original/file-20191021-56194-p4ls9f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/297831/original/file-20191021-56194-p4ls9f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/297831/original/file-20191021-56194-p4ls9f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/297831/original/file-20191021-56194-p4ls9f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/297831/original/file-20191021-56194-p4ls9f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/297831/original/file-20191021-56194-p4ls9f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Evergreen branches are built to let snow slide off them so they don’t snap under the weight.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/snow-covered-fir-trees-heavy-snowfall-764380549">Melinda Nagy/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>Conifer branch architecture is also adapted to shedding snow. Conifer branches generally sweep outwards and downwards from the trunk: Think of a Christmas fir. Not only that, conifer branches are generally more flexible than their counterparts on deciduous trees. Collecting heavy snow weighs down conifer branches until they reach an angle where it sloughs off. </p>
<p>No matter the species, at midlatitudes, where the snow flies in winter and growing seasons are generally mild and favorable, trees need strategies to make it through. Some recreate a crown of leaves each spring. Evergreens equip their needles and branches with features necessary to survive winter and thus live to see another spring – and, for some, many springs thereafter.</p>
<p>[ <em><a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=expertise">Expertise in your inbox. Sign up for The Conversation’s newsletter and get a digest of academic takes on today’s news, every day.</a></em> ]</p><img src="https://counter.theconversation.com/content/123744/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Barry Logan does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Many deciduous trees put on a dazzling fall foliage display. But coniferous evergreens hold on to their needles and stay green. A biologist breaks down these different survival strategies.Barry Logan, Professor of Biology, Bowdoin CollegeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1053182018-10-24T12:57:08Z2018-10-24T12:57:08ZCurious Kids: why do leaves change colour?<figure><img src="https://images.theconversation.com/files/241853/original/file-20181023-169834-18pfwlu.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C5841%2C3445&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/nicokaiser/30567324612/sizes/l">Nico Kaiser/Flickr.</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series for children of all ages, where The Conversation asks experts to answer questions from kids. All questions are welcome: find out how to enter at the bottom of this article.</em> </p>
<hr>
<blockquote>
<p><strong>Why do leaves change colour in autumn? – Isaac, age eight, Guildford, UK</strong></p>
</blockquote>
<p>Hi Isaac, this is a really interesting question and something that lots of people wonder about when the seasons change. In the autumn, lots of plants (especially trees) throw away their leaves. </p>
<p>These are great for jumping in, but why do some plants do this? It seems like a waste. But actually, by dropping their leaves they are saving their nutrients for the next summer. </p>
<p>For plants to grow, they need sunlight, nutrients and water. The nutrients and water come from the soil. The sunlight is captured by the leaves. </p>
<p>To capture the sunlight, the leaves use a chemical called chlorophyll, which is what makes leaves green. Chlorophyll turns sunlight into food, which the trees need to grow, through a process called photosynthesis. </p>
<p>In summer, plants do lots of photosynthesis, because they get lots of light and because it is warm. The food they make is sugar, which they use to grow new leaves, flowers and seeds.</p>
<p>In winter, things are less comfortable. The days get shorter, it gets colder and there is less sunshine. For you, this is not a problem – if you are cold, you can put a coat on. But plants can’t do this. And when it gets really cold, and freezes, their leaves can be damaged.</p>
<p>If you want to see what freezing does to different leaves, there is an experiment you can try at home. Take some different leaves and put them in your freezer, or the ice box in your fridge. Leave them for a day to get really cold, then take them out again. Put them on a plate so you don’t make a mess, then just wait for them to warm up (this will take a while). </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/241860/original/file-20181023-169834-d9qqz6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/241860/original/file-20181023-169834-d9qqz6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/241860/original/file-20181023-169834-d9qqz6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/241860/original/file-20181023-169834-d9qqz6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/241860/original/file-20181023-169834-d9qqz6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/241860/original/file-20181023-169834-d9qqz6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/241860/original/file-20181023-169834-d9qqz6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Frozen brrrries!</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/frosty-holly-green-leaves-red-berries-776253379?src=B2Y8-5tXSe3NcOcWdyUHiw-1-33">Shutterstock.</a></span>
</figcaption>
</figure>
<p>Some leaves are really tough and don’t mind being frozen. If you take a holly leaf, it will look just the same after you freeze it as it did before. But if you try this with a soft leaf, such as lettuce, you will see something different. </p>
<p>For plants with leaves that don’t like to be frozen, winter is a bad time. Their leaves are all going to be destroyed in the cold weather. If this happens, they will also lose a lot of good things which are in the leaf, especially the nutrients they get from the soil. </p>
<p>They use the nutrients to make chlorophyll and they don’t want to lose them when the leaves freeze. So instead, they break down the chlorophyll to get the nutrients out and store them in their roots, which are protected from the cold.</p>
<p>As the plants break down the chlorophyll, the green colour disappears from their leaves. What is left behind is other chemicals which you normally cannot see. The most important of these are called carotenoids, which are what makes carrots orange. </p>
<p>Depending on which chemicals are found in the leaf, they can turn different shades of yellow or orange or even red. These chemicals do not have any nutrients in them, so the plant does not bother to break them down, it leaves them in the leaves. </p>
<p>Once all the chlorophyll is taken out, the leaf dies. As it dries out, the leaf starts to look brown and becomes crispy. At this stage, it falls off the tree.</p>
<p>In the spring, as the days get longer and the weather gets warmer, the tree uses the nutrients and food that it has stored in its roots to make new leaves, ready for the summer when it can do lots of photosynthesis again.</p>
<hr>
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<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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</figure>
<p><em>Please tell us your name, age and which town or city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question, but we will do our best.</em></p>
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<p><em>More <a href="https://theconversation.com/topics/curious-kids-36782?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Curious Kids</a> articles, written by academic experts:</em></p>
<ul>
<li><p><em><a href="https://theconversation.com/curious-kids-why-do-flies-vomit-on-their-food-98555?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Why do flies vomit on their food? – Lili, age ten, Adelaide, Australia</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-if-you-have-lots-of-the-thing-youre-allergic-to-does-your-body-get-used-to-it-104881?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">If you have lots of the thing you’re allergic to, does your body get used to it? – Karen and Dawn, Manchester, UK</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-why-do-we-need-food-98938?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Why do we need food? – Milo, age five, Cowes, Australia</a></em></p></li>
</ul><img src="https://counter.theconversation.com/content/105318/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Giles Johnson receives funding from the Biotechnology and Biological Sciences Research Council. </span></em></p>Dropping leaves might seem like a waste, but plants are actually saving nutrients.Giles Johnson, Senior Lecturer in Environmental Sciences, University of ManchesterLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/998182018-07-17T10:46:56Z2018-07-17T10:46:56ZPigments from microbes provide clue to evolution in ancient oceans – but weren’t pink a billion years ago<figure><img src="https://images.theconversation.com/files/227876/original/file-20180716-44076-p499t1.jpg?ixlib=rb-1.1.0&rect=308%2C242%2C1628%2C1153&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cyanobacteria filled the ancient oceans and used chlorophyll to harvest the sun's energy.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/28594931@N03/4726914132">Specious Reasons</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>Possibly the most <a href="https://doi.org/10.1126/sciadv.1603076">significant event in the evolution of life</a> on Earth occurred 2.4 billion years ago. That was when the amount of oxygen in the atmosphere and ocean surface waters rapidly increased – setting the stage for a new phase of life on our planet.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1155&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1155&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1155&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1451&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1451&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1451&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Most of the forms of life we’re familiar with are relatively recent additions to the planet.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:LifeTimeline-TemplateImage-20170116.png">Drbogdan</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Oxygen is produced by photosynthesis, a process that evolved in a type of bacteria <a href="http://www.ucmp.berkeley.edu/bacteria/cyanointro.html">called cyanobacteria</a>. Also known – incorrectly – as blue-green algae, you can encounter them today as pond scum.</p>
<p>Cyanobacteria are prokaryotes: simple single-celled organisms. <a href="http://www.ucmp.berkeley.edu/greenalgae/greenalgae.html">True algae</a> are eukaryotes: more complex, larger organisms. Both perform the same photosynthetic reactions to turn energy from the sun into oxygen and food molecules. The first true algae, as well as other single-celled eukaryotes, arose at least 1.4 billion years ago, but, mysteriously, appear to have remained in the background of life for another 800 million years, at which point they <a href="https://doi.org/10.1042/ETLS20180039">rapidly expanded in number and diversity</a>.</p>
<p><a href="https://doi.org/10.1073/pnas.1803866115">New research</a> by Australian National University earth scientists <a href="https://nationalmaglab.org/about/around-the-lab/meet-the-users/nur-gueneli">Nur Gueneli</a>, <a href="https://scholar.google.com/citations?user=oqL0DAUAAAAJ&hl=en&oi=ao">Jochen Brocks</a> and colleagues confirms the early importance of cyanobacteria in the primordial oceans and provides insights into why it took so long for the true algae to become the base of the food chain.</p>
<h2>Billion-year-old biomarkers</h2>
<p>Much of our knowledge of evolutionary history comes from the fossil record. Unfortunately, soft-bodied organisms, such as algae, rarely leave fossils. But researchers can recover the biomolecules they contained that are resistant to degradation. Found within ancient sediments, scientists can use these molecular fossils, <a href="http://summons.mit.edu/biomarkers/what-is-a-biomarker/">called biomarkers</a>, to identify what types of organisms were present when the sediments formed.</p>
<p>The new study published in the Proceedings of the National Academy of Science examined extracts of 1.1 billion-year-old sediments from 140 to 200 meters below the surface of a site in Mauritania. This corner in northwest Africa was once covered by an ocean. The researchers didn’t detect any biomarkers indicative of eukaryotes, but did find biomarkers indicating that several types of prokaryotes had been present. So no true algae, but plenty of evidence of photosynthetic bacteria. Of particular interest, they found molecules, <a href="http://physicsopenlab.org/2016/07/04/porphyrins-the-colors-of-life/">called porphyrins</a>, that are the remains of <a href="https://www.worldofmolecules.com/colors/chlorophyll.htm">chlorophyll</a>, the molecular basis of photosynthesis.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=602&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=602&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=602&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=756&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=756&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=756&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Chemical structure of a simple porphyrin ring. The porphyrin in chlorophyll has a magnesium atom in the middle.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Porphyrin.svg">Lukáš Mižoch</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Using a clever analysis, the scientists were able to identify with near certainty what organisms were the source of the porphyrins. <a href="https://www.webelements.com/nitrogen/isotopes.html">Nitrogen has two atomic forms, called isotopes</a>, the most common of which, ¹⁴N, has an atomic weight of 14 while the rare isotope, ¹⁵N, has an atomic weight of 15. Although ¹⁴N is preferred, the various enzymes that make chlorophyll also incorporate ¹⁵N in proportions that differ among different classes of photosynthetic organisms. So the ratio of ¹⁴N to ¹⁵N in porphyrin molecules, which have four nitrogen atoms, can indicate what type of organism produced them. By measuring the N-isotope ratios in the porphyrins from the sediments, the scientists were able to trace the molecules to the cyanobacteria.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A vial of pink-colored porphyrins recovered from sediments that are more than a billion years old.</span>
<span class="attribution"><a class="source" href="http://dx.doi.org/10.1073/pnas.1803866115">The Australian National University</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Not pink, but green</h2>
<p>A dramatic picture in the Gueneli paper showed that some of the extracts of the ancient sediments were brilliant pink. News coverage ran with headlines focused on Earth’s “oldest color” being bright pink. But that’s not quite right.</p>
<p>In order to do its chemical job, the porphyrin in chlorophyll contains a magnesium atom that’s responsible for its green color. This is what makes leaves and algae look green. But in these pink extracts, the porphyrin turned out to have a nickel atom instead. Most likely the nickel replaced the magnesium sometime over the billion-plus years the molecules <a href="https://doi.org/10.1098/rstb.1991.0083">aged in the sediments</a>.</p>
<p>So pink was not the original color of the chlorophyll. It must have been green, as it is in living plants today.</p>
<h2>Algae take over from bacteria</h2>
<p>The researchers’ major conclusion is that 1.1 billion years ago, photosynthetic bacteria, most likely dominated by cyanobacteria, were the base of the food chain in the ocean. Because the bacteria were small, they would sink slowly and be degraded by other bacteria high in the water column. Little of the precious nutrients they contained would reach the ocean bottom.</p>
<p>Nutrient distribution throughout an ocean depends upon <a href="https://oceanservice.noaa.gov/facts/upwelling.html">upwelling from the bottom</a>. So most of the ocean would be nutrient-poor, restricting the development of a community of larger organisms.</p>
<p>In addition, cyanobacteria survive better than eukaryotic algae when nutrients are low, which would further <a href="https://doi.org/10.1042/ETLS20180039">restrict the evolution of these larger-celled photosynthetic organisms</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=404&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=404&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=404&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=508&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=508&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=508&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">True algae have larger and more complex cells than the cyanobacteria they took over from.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/noaaphotolib/9787178153">NOAA MESA Project</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>What caused the shift about 650 million years ago from an ocean dominated by cyanobacteria to one dominated by true algae? One of the authors of the PNAS paper, geobiologist Jochen Brocks, points out in a recent review article that this shift occurred a mere <a href="https://doi.org/10.1042/ETLS20180039">4 million years after the end of a worldwide glaciation</a>, during which the oceans were frozen for more than 50 million years. Then the glaciers melted, probably because rising carbon dioxide levels created a greenhouse effect, heating the Earth. The temperature of the oceans rose rapidly, possibly killing many remaining cyanobacteria. In addition, as the glaciers melted, vast amounts of nutrients would have been swept into the oceans, reversing the competitive disadvantage for the algae, that then were able to evolve and expand.</p>
<p>With the arrival of these larger, rapidly-settling algae as the basis of the food chain, the stage was set for the evolution and expansion of larger eukaryotic consumers.</p><img src="https://counter.theconversation.com/content/99818/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Patricia L. Foster receives funding from the US Army Research Office. She is a member of the American Association for the Advancement of Science, Union of Concerned Scientists and Concerned Scientists at IU.</span></em></p>Did you recently hear news that Earth’s oldest pigments were hot pink? That’s not quite right. When they were in living bacteria a billion years ago, they were performing photosynthesis – and green.Patricia L. Foster, Professor Emerita of Biology, Indiana UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/861602018-01-14T19:03:01Z2018-01-14T19:03:01ZCurious Kids: Why are leaves green?<figure><img src="https://images.theconversation.com/files/197524/original/file-20171204-17064-t7ilgw.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The leaves of most plants are green because the leaves are full of green chemicals.</span> <span class="attribution"><span class="source">Marcella Cheng/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!</em> </p>
<hr>
<blockquote>
<p><strong>Why are leaves green? – Indigo, age 6, Elwood.</strong> </p>
</blockquote>
<p>The leaves of most plants are green, because the leaves are full of chemicals that are green. </p>
<p>The most important of these chemicals is called “chlorophyll” and it allows plants to make food so they can grow using water, air and light from the sun.</p>
<p>This way that a plant makes food for itself is called “photosynthesis” and it is one of the most important processes taking place on the whole planet.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/197526/original/file-20171204-17082-1m7wr64.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/197526/original/file-20171204-17082-1m7wr64.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/197526/original/file-20171204-17082-1m7wr64.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=784&fit=crop&dpr=1 600w, https://images.theconversation.com/files/197526/original/file-20171204-17082-1m7wr64.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=784&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/197526/original/file-20171204-17082-1m7wr64.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=784&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/197526/original/file-20171204-17082-1m7wr64.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=986&fit=crop&dpr=1 754w, https://images.theconversation.com/files/197526/original/file-20171204-17082-1m7wr64.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=986&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/197526/original/file-20171204-17082-1m7wr64.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=986&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One of the most important chemicals on Earth is called chlorophyll. It’s green and it allows plants to make food so they can grow.</span>
<span class="attribution"><span class="source">Marcella Cheng/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Without photosynthesis there would be no plants or people on Earth. Dinosaurs would not have been able to breathe and the air and oceans would be very different from those we have today. So the green chemical chlorophyll is really important. </p>
<p>All leaves contain chlorophyll, but sometimes not all of the leaf has chlorophyll in it. Some leaves have green and white or green and yellow stripes or spots. Only the green bits have chlorophyll and only those bits can make food by photosynthesis.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/198456/original/file-20171211-27683-nbdqnj.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/198456/original/file-20171211-27683-nbdqnj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/198456/original/file-20171211-27683-nbdqnj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=668&fit=crop&dpr=1 600w, https://images.theconversation.com/files/198456/original/file-20171211-27683-nbdqnj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=668&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/198456/original/file-20171211-27683-nbdqnj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=668&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/198456/original/file-20171211-27683-nbdqnj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=840&fit=crop&dpr=1 754w, https://images.theconversation.com/files/198456/original/file-20171211-27683-nbdqnj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=840&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/198456/original/file-20171211-27683-nbdqnj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=840&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">All leaves contain chlorophyll, but sometimes not all of the leaf has chlorophyll in it.</span>
<span class="attribution"><span class="source">Marcella Cheng/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>If you’re really good at noticing things, you might have seen plants and trees with red or purple leaves – and the leaves are that colour all year round, not just in autumn.</p>
<p>These leaves are still full of our important green chemical, chlorophyll, just like any other ordinary green leaf. However, they also have lots of <em>other</em> chemicals that are red or purple – so much of them that they no longer look green. But deep down inside the leaves the chlorophyll is still there and it’s still green.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/198449/original/file-20171211-27719-18sz2ir.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/198449/original/file-20171211-27719-18sz2ir.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/198449/original/file-20171211-27719-18sz2ir.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=342&fit=crop&dpr=1 600w, https://images.theconversation.com/files/198449/original/file-20171211-27719-18sz2ir.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=342&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/198449/original/file-20171211-27719-18sz2ir.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=342&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/198449/original/file-20171211-27719-18sz2ir.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=429&fit=crop&dpr=1 754w, https://images.theconversation.com/files/198449/original/file-20171211-27719-18sz2ir.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=429&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/198449/original/file-20171211-27719-18sz2ir.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=429&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Even leaves that don’t look green have chlorophyll. However, they also have lots of other chemicals that are red or purple.</span>
<span class="attribution"><span class="source">Marcella Cheng/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:</em></p>
<p><em>* Email your question to curiouskids@theconversation.edu.au
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* Tell us on <a href="https://twitter.com/ConversationEDU">Twitter</a> by tagging <a href="https://twitter.com/ConversationEDU">@ConversationEDU</a> with the hashtag #curiouskids, or
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<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em>Please tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/86160/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gregory Moore does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky! Why…Gregory Moore, Doctor of Botany, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/649372016-09-08T08:28:51Z2016-09-08T08:28:51ZWhy you can expect a spectacular autumn<figure><img src="https://images.theconversation.com/files/136867/original/image-20160907-25272-m66f49.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Whether you think autumn officially starts at the beginning or end of September, you only have to look at the trees to see the season is changing. Leaves on deciduous trees always change colour from green to vibrant hues of yellow, orange, and red. But some years the colourful show is more spectacular than others. One of the most outstanding recent years in <a href="http://www.telegraph.co.uk/news/uknews/3256175/Best-autumn-colours-on-trees-for-years.html">the UK was 2008</a>. And the Forestry Commission is expecting 2016 to be <a href="http://www.forestry.gov.uk/newsrele.nsf/AllByUNID/0FE1C5B5C41167528025801400350FEA">another one of the best</a>. </p>
<p>So what produces an autumn to remember? Variation from one year to the next in nature can be seen in a number of phenomena, such as the amount and duration of spring blossom or the quantity of fruit and berries on bushes and trees. Oenophiles (wine lovers) will know that the quality of grapes from which wine is made varies from one year to another. The underlying explanation for all these phenomena is basically the same: the weather.</p>
<p>The distinctive autumnal woodland colours in leaves are formed by the combination of four classes of chemicals: chlorophyll, carotenoids, xanthophylls, and anthocyanins. Chlorophyll, the main chemical involved in photosynthesis, reflects green light, which explains the green colour of most deciduous trees in spring and summer. </p>
<p>As the days shorten in temperate latitudes, trees prepare for their winter dormant period by withdrawing nutrients from their leaves. Chlorophyll is rich in nitrogen. While some chlorophyll breaks down throughout the year, the <a href="http://www.usna.usda.gov/PhotoGallery/FallFoliage/ScienceFallColor.html">process accelerates during autumn</a>. As less green light is reflected, the colours of other chemicals in the leaves become visible.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=373&fit=crop&dpr=1 600w, https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=373&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=373&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=468&fit=crop&dpr=1 754w, https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=468&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=468&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Chlorophyll, xanthophylls, carotenoids and anthocyanins.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Changing pigments</h2>
<p>Carotenoids, another chemical involved in photosynthesis, tend to be orange. The yellow xanthophylls are oxygenated carotenoids. The many anthocyanin compounds produce a palette of reds, ranging from the brightest scarlet to maroons and purple. Put these colours together and you have a vibrant patchwork of colour clothing the countryside, urban parks and gardens.</p>
<p>Data from the Met Office show that August 2016 was warmer (by 0.6°C) and sunnier (110%) <a href="http://www.metoffice.gov.uk/climate/uk/summaries">compared to the long-term average</a>. Combined with a wet spring (rainfall 30% above average in the east and south), this will have led to higher than average levels of sugars in plant tissues – and it is these sugars that are the real key to the richness of the autumnal colours. Anthocyanins are large, complex molecules containing a sugar, usually glucose. So more sunshine means more glucose, more anthocyanins and more vibrant autumnal colours in 2016.</p>
<p>Anthocynanins are produced by some species of tree but not by others and they are also important in the production of the intense colours of many fruits and berries, including the colour of red grapes. In leaves, as the level of chlorophyll decreases, anthocyanins are produced.</p>
<p>It is still not absolutely clear what function is performed by anthocyanins. It costs the plant energy to make them and only some tree species produce anthocyanins. Around <a href="http://bit.ly/2c6uTOk">15% to 30%</a> of tree leaf colour is caused by carotenoids and xanthophylls alone. There is <a href="http://onlinelibrary.wiley.com/doi/10.1046/j.1365-3040.2002.00905.x/abstract;jsessionid=ADFE382A48655FD323BCD47C2AC0872E.f01t01">some suggestion</a> that anthocyanins are antioxidants and perform a protective role by preventing free radicals (reactive atoms or molecules) from destroying plant tissue and DNA. But this explanation is not universally accepted. </p>
<p>Other explanations are that anthocyanins <a href="http://research.haifa.ac.il/%7Ebiology/simcha/Publications/PIB17.pdf">effectively mask the leaves</a> visually from some predators that can see the green leaves but do not possess the photoreceptors required to detect red leaves or insects that find red less attractive than green.</p>
<p>As the chlorophyll breaks down and leaves naturally turn yellow and orange, so that the carotenoids and xanthophylls are no longer masked by the green, they attract sap-sucking aphids. So some species of tree produce a bright red pigment in the leaves to confuse insects.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The hunt for red October.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>How long will it last?</h2>
<p>Although the summer weather means we can expect an impressive autumn, there are still some questions. Will 2016 be a long autumnal season, stretching from mid-September into November – or will it be cut short? In 2008, there were a few early frosts. Frost promotes abscission, the process by which the leaf detaches from the twig.</p>
<p>In 2008, leaves fell from the trees over a <a href="http://www.telegraph.co.uk/news/uknews/3256175/Best-autumn-colours-on-trees-for-years.html">relatively short period</a> of time. That, of course, brings with it the joys of kicking through piles of fallen leaves, but an early frost will shorten the duration of the autumnal show, as might the high winds associated with autumnal storms.</p>
<p>In the absence of early frosts and storms, however, we can look forward to a magnificent display. But for how many more years will this continue? Climate change has seen the onset date of leaf colour change <a href="http://www.bbc.co.uk/earth/story/20140929-why-is-autumn-changing">being pushed back</a>. That narrows the window during which the colours can be seen and enjoyed. If we are lucky this year, we will see a peak of colour in mid to late October with leaves still on the trees in November – but watch the weather forecast for the latest.</p><img src="https://counter.theconversation.com/content/64937/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Philip James does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Here’s the science behind the amazing colours we should see on British trees this year.Philip James, Professor of ecology, University of SalfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/320122014-10-21T09:52:14Z2014-10-21T09:52:14ZFall foliage in the crosshairs of climate change<figure><img src="https://images.theconversation.com/files/60803/original/mnj3gxc3-1412364346.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Enjoy the color while you can before climate change makes a mess of this too.</span> <span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:Vermont_fall_foliage_hogback_mountain.JPG">chensiyuan</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>One of nature’s most spectacular events occurs every autumn, when the leaves of hardwood trees burst into brilliant color before falling to the ground. These autumnal displays in the eastern United States, Europe, eastern Asia and a few locales in South America and New Zealand entice people to experience nature in all its raw beauty.</p>
<p>Leaf peeping can pump hundreds of millions of <a href="http://www.uvm.edu/%7Esnrvtdc/publications/2001_Fall_Foliage_Report.pdf">tourist dollars</a> into the economies of particularly colorful areas. But now climate change hovers in the background, threatening to alter future versions of this annual color show.</p>
<h2>Business as usual</h2>
<p>Tree leaves turn color in the fall in response to shorter days and cooler temperatures. In August and September, trees begin an <a href="http://www.plantphysiol.org/content/139/4/1635.short">orderly process</a> of leaf senescence – or dying – characterized by the loss of chlorophyll. That’s the green pigment that plants use to capture light for photosynthesis.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Red and yellow now … brown in the future?</span>
</figcaption>
</figure>
<p>Some species, such as <a href="http://www.plantphysiol.org/content/127/2/566.short">dogwoods</a>, red maples and red oaks, begin to make <a href="http://treephys.oxfordjournals.org/content/21/1/1.short">anthocyanins</a>, the pigments that give leaves their bright red color. Other trees, such as birches, tulip poplars and beech, don’t make anthocyanins. Instead, when their chlorophyll breaks down, pigments hidden during the summer months become visible. Called carotenoids and xanthophylls, they’re the pigments responsible for producing orange and yellow leaves. </p>
<h2>Too warm, too cool</h2>
<p>If the <a href="http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0057373#pone-0057373-g005">fall is cool</a>, trees develop leaf color earlier. Warmer years, the display of color is <a href="http://onlinelibrary.wiley.com/doi/10.1111/geb.12206/full">delayed</a>. In a world warmed by climate change, the onset of colors would always come later in the season. Some trees are more sensitive to temperature than others. As the climate warms, the finely-tuned timing of the fall’s color display may lose its <a href="http://rstb.royalsocietypublishing.org/content/365/1555/3247.short">synchronization</a>. Rather than the well-timed symphony of color that we’re used to now, we might see unsynchronized patches as each species changes over the course of the season.</p>
<p>Warmer temperatures may also allow pests such as insects, fungi or bacteria – not to mention exotic tree species such as the Princess Tree – to move farther north than usual. These pests could alter the composition of the forest, much as when chestnuts were eliminated by blight 100 years ago. If the species composition of future forests changes in response to climate change, the quality of the fall foliage display will be quite different from what we see now.</p>
<h2>Sugars from sun</h2>
<p>Sunshine plays a role here too. Later in the season, the days are shorter and the sun is lower in the sky due to the earth’s tilt. This reduced sunlight slows down the process of photosynthesis and lowers sugar reserves. Without those sugars to stimulate the synthesis of anthocyanins, we get duller red leaves.</p>
<h2>Too wet, too dry</h2>
<p>Global climate change might also alter precipitation amounts and timing. Too much rain lowers the intensity of fall color – not because it washes out the colors (an old wives’ tale), but rather because cloudy skies and low light cut down on photosynthesis and production of those vital anthocyanins. Conversely, drought causes trees to drop their leaves prematurely before they get a chance to turn color.</p>
<p>Nitrogen is another <a href="http://treephys.oxfordjournals.org/content/23/5/325.short">factor</a> that could mute the color display. Excess levels, which can result from pollution and increased precipitation, also reduce anthocyanin production. Again the result is less red leaf color. We may already be seeing less vibrant red fall displays than those prior to industrialization, since most eastern <a href="http://nadp.sws.uiuc.edu/committees/tdep/tdepmaps/preview.aspx#n_td">forests today</a> get from two to seven times the natural input of nitrogen.</p>
<h2>Migrating trees</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fall foliage display as seen from space.</span>
<span class="attribution"><a class="source" href="http://earthobservatory.nasa.gov/IOTD/view.php?id=1893&eocn=image&eoci=related_image">NASA’s Earth Observatory</a></span>
</figcaption>
</figure>
<p>If it becomes too warm or too dry for some tree species, they may have to migrate to more suitable habitats. Individual trees, of course, can’t pick up and move in response to climatic conditions. But the trees in inhospitable areas would die out and seedlings would take hold in new cooler areas. </p>
<p>In Vermont, where temperatures have increased by 2.5F (1.5C) in the past 50 years, hardwood trees have <a href="http://www.pnas.org/content/105/11/4197.short">migrated</a> around 328ft (100m) upslope, where it’s cooler. For trees on flatter terrain, warmer temperatures will force them to migrate north. Sugar maple, one of the major fall color trees in New England, may <a href="http://www.sciencedirect.com/science/article/pii/S0378112707005439">move</a> right out of the United States into Canada. What will autumn in New England feel like without the brilliant red colors we’re used to? Such migrations will alter the <a href="http://www.nrs.fs.fed.us/atlas/tree/">composition of our forests</a> forever. A new fall color balance will eventually emerge. </p>
<h2>Don’t forget carbon dioxide</h2>
<p>Of course, an increase in the amount of carbon dioxide in Earth’s atmosphere is one of the reasons the climate is warming in the first place. Trees will need to adapt as carbon dioxide levels continue to rise over the coming decades. <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2010.03184.x/full">Research</a> suggests that more CO<sub>2</sub> might actually enhance fall colors. So score one point for global warming – even if this one factor won’t tip the balance.</p>
<h2>Catch this show while you can</h2>
<p>Global climate change will not eliminate fall leaf color, but the best displays will move northward and upward in elevation in response to warming. For forests in their present location, fall foliage displays will occur later in the season and may last longer, but will be of diminished quality due to less intense red colors. The fall foliage displays that our grandchildren will see at the end of this century will not be the ones we see today.</p><img src="https://counter.theconversation.com/content/32012/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Howard Neufeld does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>One of nature’s most spectacular events occurs every autumn, when the leaves of hardwood trees burst into brilliant color before falling to the ground. These autumnal displays in the eastern United States…Howard Neufeld, Professor of Physiological Plant Ecology, Appalachian State UniversityLicensed as Creative Commons – attribution, no derivatives.