abscission The rejection of plant organs, e.g. of leaves in autumn. This occurs at an abscission zone, where hydrolytic enzymes reduce cell adhesion. The process can be promoted by abscisic acid and inhibited by respiratory poisons, and is controlled in nature by the proportion and gradients of auxin and ethylene. Other hormones may be involved.

abscission 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 growth substance, 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.

ab·scis·sion / abˈsizhən/ • n. Bot. the natural detachment of parts of a plant, typically dead leaves and ripe fruit. ∎  any act of cutting off.

abscission The rejection of plant organs (e.g. of leaves in autumn). This occurs at an abscission zone, where hydrolytic enzymes reduce cell adhesion. The process can be promoted by abscisic acid and inhibited by respiratory poisons, and is controlled in nature by the proportion and gradients of auxin and ethylene. Other hormones may be involved.