Leaf abscission
/lif æbˈsɪʒən/
Definition
Leaf abscission is the natural, regulated process by which a plant sheds a leaf at a specialized separation zone, called the abscission zone, near the base of the leaf stalk. Cells in this zone weaken and separate, then a protective layer forms over the exposed tissue. It differs from leaves dropping because of breakage or disease alone. Seasonal leaf fall in deciduous trees is a common example of leaf abscission.
Biological Role
- Seasonal energy savings: In many deciduous plants, leaf abscission helps reduce water loss and metabolic demand before winter or dry periods, when keeping older leaves would cost more resources than they return.
- Protected separation point: The process occurs at an abscission zone, a specialized layer of cells near the leaf base. Cells there weaken in a controlled way, which helps detach the leaf while sealing exposed tissue.
- Hormone-driven timing: Plant hormones help regulate timing. Ethylene generally promotes separation, while auxin, a growth signal made in active tissues, tends to delay it when present at higher levels.
- Stress response clue: Drought, flooding, low light, nutrient imbalance, pests, disease, or sudden environmental change can trigger early leaf abscission. In cultivation, unusual leaf drop often signals that growing conditions need review.
Related Terms
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