Why do leaves change from green to yellow in the fall?
Nathan Kleist, Jonathon Hungerford CU Boulder, Fall 2008 In the autumn, leaves change from green to yellow. This trademark of shorter and colder days is a sign that the plant is getting ready for the impending winter. Plants prepare for this change by breaking down chlorophyll from the leaves for nutrients. With the green chlorophyll out of the way the carotenoids become the visible pigments and the leaves turn yellow. Why dont the plants dissolve the carotenoids? We hypothesize that leaves turn yellow in the fall because the green chlorophyll are absorbed while the yellow carotenoids stay in place for photoprotection. If carotenoids are photoprotectors, while under blue light, there should not be a high rate of photosynthesis in yellow leaves or a very high rate of photosynthesis in green leaves. Also if carotenoids are photoprotectors there should be low rates of photosynthesis from yellow leaves under red light and practically no photosynthesis from yellow leaves under blue light. T
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