Scott Rushing, 11, of Winston Salem, N.C., for his question:

WHY DO LEAVES CHANGE COLOR IN AUTUMN?

As summer comes to an end each year, a disk of cork cells in many tree leaves grows to block the pipelines to and from the leaf. When the vein system of the leaf is finally completely cut off from water, the leaf stops making food. At the same time, the chlorophyll in the leaf begins to break down and other beautiful colors that had been hidden are revealed.

With its flow of raw material suddenly cut off, the leaf loses its green color and reveals hidden yellow, orange, red and purple tones.

A leaf's autumn color will depend on its compounds. It will be yellow if its pigment is xanthophyll, orange if the leaf contains carotene and red or purple if a compound called anthocyanin is part of the makeup.