Hey everyone,
I was wondering if anyone could explain to me like I’m five why leaves change color in the fall. I know it has something to do with the temperature and the amount of sunlight, but I’m not sure how that makes the leaves turn red, yellow, and orange.
Thanks in advance for any explanations!
In: 11
This is an adaptation by trees in order to reduce evaporation during winter. When the ground freezes the tree roots are unable to get water and the tree might end up drying up over the winter. Most of the water loss is by evaporation in the leaves. Some trees will therefore shead their leaves in the autumn. The problem is that the green of the leaves, the chlorophill, requires a lot of minerals to make. So if the trees just sheaded the leaves they would likely end up with mineral deficiancy in the sping. They therefore absorb back all the green in their leaves before they shead them. This just leaves the raw structure of the leaves which is mostly cellulose and have a yellow/red/brown color to them.
In colder climate it is impossible to save leaves through winter, they would die and start to decompose which would make them entry point for disease and cause problems and possibly kill plant. So instead of waiting for them to die, they are being recycled as much as possible and separated from plant, so that un-recyclable leftover would fall off plant. Chemicals that make leaves green are fully recycled, so leftover has color of whatever is left.
Trees remove chlorophyll from the leaves for winter storage elsewhere because it’s not that easy to make and shedding it along with leaves would be a waste of a scarce resource. Chlorophyll is the compound which plants use to extract energy from sunlight and coincidentally it is what makes leaves green.
Leaves are green because there’s a chemical called chlorophyll in them that makes them green. Chlorophyll is important because it absorbs sunlight which the plant uses (photosynthesis: light + water + carbon dioxide = sugar).
In the fall, the amount of light starts to go down and the tree is not making a lots of food, so it starts to shutdown. It stops making chlorophyll first, and the green color fades away. What you see is whatever’s left over (and that varies by the variety of tree). There are chemicals called carotenoids that are yellow and orange, and others called anthocyanins which are deep red. You begin to see the color from those chemicals in the leaves now that the green is gone…. until the temperature drops and the leaves start to die off, at which point the leaves begin to dry up the other colors also fade.
Leaves change color because they die.
Or rather, because tree kills them to save energy/nutrients for the winter. Leaves have tubes in them much like human blood vessels, which connect to tree. Tree starts sending a kind of resin that will eventually build up and clog up the vessel, and cut leaf off from circulation, so leaf won’t get nutrients from tree anymore. And without them, it won’t produce chemical which gives color to the leaf, and dries up.
Leaves change color in the fall because of a complex chemical process that occurs in the cells of the leaves. During the spring and summer, leaves are able to produce a green pigment called chlorophyll, which helps the plant to capture sunlight and convert it into energy through the process of photosynthesis.
As the days get shorter and the weather gets colder in the fall, the plant begins to shut down its photosynthetic processes and stop producing chlorophyll. This allows other pigments in the leaves, such as carotenoids and anthocyanins, to become more visible. These pigments give the leaves their yellow, orange, and red colors.
The exact colors that a leaf will turn in the fall depends on the mix of pigments present in the leaf and the amount of sunlight and moisture the plant receives. The colors of fall leaves are also influenced by the temperature and other environmental factors, which can cause the leaves to change color faster or slower.
ELI5 Version: You know how if you hock a loogie Juuuust right you can suck it all the way back up into your mouth?
Well imagine the green in trees is the loogie and the tree sucks it back up. That just leaves the rest of the leaf which is like a reddish-brownish color depending on species and that’s just because of the specific way each tree makes its leaves.
Deciduous trees undertake a form of hibernation during winter.
Big, flat green leaves are great in the summer as they can absorb a lot of light to provide energy for the tree. In the winter however those same leaves become a handicap – the shorter days and colder sun means there isn’t as much light to absorb, and they start to be at risk of damage from cold temperatures and freezing.
So the trees essentially hibernate – they stop trying to grow their leaves and let them die and fall off so they can hunker down and save their energy to regrow in the spring.
The leaves turn brown because they die – the chlorophyll that creates the bright green colour stops being grown and maintained, and turns brown, then once the leaf has died off completely and no longer helps the tree, it falls off.
Not all trees do this however – in places close to the equator where it is always reasonably warm, trees will stay green and leafy year round, with leaves constantly falling off and being replaced through the year.
In more northern climates we also have evergreen trees like the pine that have adapted to the cold weather – rather than large, flat, cold susceptible leaves, they have much smaller and thinner needles that can better survive the child and stay green year round.
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