Opinion 3 (from “Why Leaves Turn Color in the Fall” by Diane Ackerman): Leaves have always hidden our awkward secrets.
Autumn is a season of beautiful leaves, which come from sunlight and chlorophyll breaking down. Animals migrate, hibernate, or store food to prepare for winter, but trees survive by dropping their leaves. Fall foliage is spectacular in the northeastern US and eastern China due to its rich climate. Anthocyanin, the pigment that gives apples their red, varies from year to year depending on the temperature and amount of sunlight. Leaves color beautifully in the fall, symbolizing death and disintegration, as Nature becomes more carnal, mute, and radiant. Leaves fall from the trees due to the growth hormone, auxin, and division of cells at the base. Leaves remind us of the end of a season and the end of life, turning color, crunching, crackling, and clinging to one's feet.
(Hope this helps!)