The shedding of leaves as a result of the formation of a zone of *abscission
at the base of the petiole. Leaves on dead branches do not fall as no such zone is produced. In deciduous plants there is a continual shedding of older leaves throughout the growing season but with the onset of the winter or dry season there is a conspicuous shedding of all the remaining leaves. In evergreens leaves are shed and replaced continually and there is no period when the plant is devoid of foliage. Leaf fall is associated with a drop in the auxin level of the lamina.