Why do tree leaves turn colors in the fall?
Trees absorb their chlorophyll molecules during autumnal months to keep them from being lost as leaves fall from the tree. Unlike carotenoids, which are easily replaced with new leaf growth, chlorophyll takes a tremendous amount of energy to produce. By withdrawing it back into the trunk over the winter, the tree can save its energy for spring growth, when the chlorophyll will be sent back into the leaves so photosynthesis can occur.
