abscission


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Related to abscission: abscission layer, abscission zone

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 ?
divergens was more affected by the dry season than by flooding due to low soil water content, leaf abscission and flower production.
However, after 8 weeks of culture, necrosity, leaf epinasty, leaf abscission and hiperhidricity were observed in both, Granola and Arbolona negra cultures both in semi-solid and liquid culture.
As the cells in the abscission layer become drier and more cork-like, it creates a barrier to the transport of minerals and other substances into the leaf.
Cutting the twig from the tree stopped not only the growth process of the twig and leaves but also its ability to change the abscission layer between the twig and the petiole, which was necessary in order for the leaves to fall.
Costs and benefits of flower abscission and fruit abortion of Asclepias speciosa.
High callogenesis was observed in all the combinations at the bases of explants with leaf abscission in the regenerated shoots.
The best vegetative growth is possible with temperatures varying from 21 to 33[degrees]C, while higher temperatures can cause earlier flowering and flower abscission, resulting in poor pod set.
Some authors have held that these features represent cone abscission scars, others that they are the result of branch abscission.