Britannica Sources used in this answer

How do cell wall-degrading enzymes contribute to leaf drop in autumn?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Cutaway illustration of a plant cell showing labeled internal structures including the nucleus, nucleolus, chloroplast, mitochondrion, vacuole, endoplasmic reticulum, ribosomes, Golgi apparatus, cell wall, and other key organelles. — Cell wall Cutaway drawing of a plant cell, showing the cell wall and internal organelles.

In the context of plant anatomy, the process of autumnal leaf drop is a highly controlled biological event rather than a random occurrence. As temperatures cool and day length decreases, plants initiate the formation of an abscission layer between the leaf stalk and the twig.1

The actual separation of the leaf from the plant is facilitated by cell wall-degrading enzymes. These enzymes break down the structural components of the cell walls within the abscission layer, effectively weakening the connection between the leaf and the stem. By systematically degrading these walls, the plant can cleanly detach the leaf without leaving an open wound, allowing the plant to enter dormancy while protecting its physical integrity against winter conditions like wind and snow.231