The separation of a leaf, fruit, or other part from the body of a plant. It involves the formation of an abscission zone, at the base of the part, within which a layer of cells ( abscission layer) breaks down. This process is suppressed so long as sufficient amounts of auxin, a plant hormone, flow from the part through the abscission zone. However, if the auxin flow declines, for example due to injury or ageing, abscission is activated and the part becomes separated. Ethylene acts as the primary trigger for abscission, inducing cells in the abscission zone to produce cellulase enzymes that degrade cell walls.
Subjects: Biological Sciences.