leaf or fruit drop induced by hormonal changes.
Merriam-Webster Online Dictionary
abscission (noun)1.
the act or process of cutting off - removal
2.
the natural separation of flowers, fruit, or leaves from plants at a special separation layer
abscission (Wikipedia)
Abscission (from Latin ab, "away", and scindere, "to cut'") is the shedding of various parts of an organism, such as a plant dropping a leaf, fruit, flower, or seed. In zoology, abscission is the intentional shedding of a body part, such as the shedding of a claw, husk, or the autotomy of a tail to evade a predator. In mycology, it is the liberation of a fungal spore. In cell biology, abscission refers to the separation of two daughter cells at the completion of cytokinesis.