Eli5 : What determines the color a tree changes in fall?
In: 5
The two main chlorophyll pigments in leaves (chlorophyll a and b) absorb light at high and low wavelengths (red and blue) in order to power the process of photosynthesis and fixation of CO2 into sugars. These pigments don’t absorb green light very well, so green light is reflected and transmitted which is why most plants appear green. During the fall/winter, there is less sunlight and the light capturing process of plants goes down. The two chlorophyll pigments degrade and aren’t maintained in the leaves, however there is a third category of pigments known as carotenoids that only absorb blue-green wavelengths, and this pigment isn’t degraded. As a result, red/yellow light starts to be reflected and transmitted as well when the chlorophyll pigment levels go down, and so the leaves change color. Leaves don’t turn blue because the carotenoids stay present throughout the year.
Latest Answers