Senescence


In the fall, annual plants and most perennials end up with dead leaves due to redistribution of nutrients to reproductive parts. Senescence is all of the processes leading to the death of a plant or some of its parts. Senescence is influenced by a decrease in daylight, wounds, drought, or nutritional deficiencies.

This video from the Plants in Motion web site illustrates senescence of day lily.

The dropping of leaves, flowers, or fruits is called abscission. Auxin production declines, cells in an abscission zone produce ethylene, and enzymes digest cell walls that attach the leaf or fruit to the plant.

Dormancy

Dormancy is a predictable period of metabolic inactivity. In autumn, daylength shortens and growth stops in many trees and nonwoody perennials. It will not resume until spring. Seeds and buds respond to environmental cues by resuming growth. This may require exposure to low temperatures for some interval and probably involves gibberellins and abscisic acid.

REVIEW: All the processes that lead to the death of a plant or any of its organs are called

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