abscission

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Abscission

The process whereby a plant sheds one of its parts. Leaves, flowers, seeds, and fruits are parts commonly abscised. Almost any plant part, from very small buds and bracts to branches several inches in diameter, may be abscised by some species. However, other species, including many annual plants, may show little abscission, especially of leaves.

Abscission may be of value to the plant in several ways. It can be a process of self-pruning, removing injured, diseased, or senescent parts. It permits the dispersal of seeds and other reproductive structures. It facilitates the recycling of mineral nutrients to the soil. It functions to maintain homeostasis in the plant, keeping in balance leaves and roots, and vegetative and reproductive parts.

In most plants the process of abscission is restricted to an abscission zone at the base of an organ (see illustration); here separation is brought about by the disintegration of the walls of a special layer of cells, the separation layer. The portion of the abscission zone which remains on the plant commonly develops into a corky protective layer that becomes continuous with the cork of the stem.

Diagrams of the abscission zone of a leafenlarge picture
Diagrams of the abscission zone of a leaf

Auxin applied experimentally to the distal (organ) side of an abscission zone retards abscission, while auxin applied to the proximal (stem) side accelerates abscission. The gibberellins are growth hormones which influence abscission. When applied to young fruits or to leaves, they tend to promote growth, delay maturation, and thereby indirectly prevent or delay abscission. Abscisic acid has the ability to promote abscission and senescence and to retard growth. Small amounts of ethylene have profound effects on the growth of plants and can distort and reduce growth and promote senescence and abscission.

abscission

[ab′sizh·ən]
(botany)
A physiological process promoted by abscisic acid whereby plants shed a part, such as a leaf, flower, seed, or fruit.
References in periodicals archive ?
In this case, the biomass of the leaves was not considered, as an infestation of spider mites (Family: Tetranychidae) destroyed some of the leaves, and other leaves had senesced and abscised by the end of the experiment.
Abscised peaches were collected at Byron, GA, in 2004 and placed on trays with mesh bottoms over a large aluminum funnel (0.
After water-stress sampling, plants were rehydrated and allowed to recover for 1 wk, at which time each plant was mapped and the number and location of bolls, squares, incompletely abscised fruit, and aborted positions were recorded.
Damaged and infested lanterns are often abscised by the plant and heavily infested plants usually have a large number of lanterns on the ground.
1995) or retained in abscised flowers or microstrobili will not travel far from the source.
For example, insect mines or galls are more likely to be abscised in young cottonwood or willow tissue than are more mature tissue, resulting in induced resistance (Williams and Whitham 1986, Preszler and Price 1993).
Fruiting forms may have been lost in such large numbers because of high temperatures that manual removal merely eliminated flowers that would have abscised due to high temperature stress.
We monitored focal individuals of the 10 plant species at weekly intervals during each summer for the presence of 6 phenological stages: unopened buds (recorded as stage 1), open flowers (stage 2), old flowers (stage 3 [post-anthesis but with petals, tepals, or petaloid sepals still attached]), initiated fruit (stage 4 [petals abscised but ovaries unexpanded]), expanding fruit (stage 5 [ovaries enlarged]), and dehisced fruit (stage 6).
2) Simulated predation - before seeds matured and infructescences abscised, seeds were removed by pulling all of the seeds ont of the primary infructescence by hand to simulate predation.
dagger]) Amount of N contained in aboveground biomass and abscised plant debris at maturity.