area at the base of the petiole where cellular breakdown leads to leaf and fruit drop.
abscission zone (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.
Leaf litter on the forest floor. Annual autumn leaf drop in temperate zones is caused by the abscission of the mature leaves from the growth season in response to the approach of cold winter weather.