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 general, fruit abscission percentage remained low during shelf life observations of all treatments (Figure 1C and Figure 1D), this research confirmed the low fruit abscission on 'Calypso' and higher rates of fruit abscission on 'MG 302' previously identified by SEGATTO et al.
Caption: Figure 1--Accumulated abscission in leaves (A, B) and fruits (C, D) of the ornamental pepper cultivars 'Calypso' and 'MG 302', after being treated with ethylene 48 hours, 1-MCP, 1-MCP + ethylene for 48 hours, STS and STS + ethylene for 48 hours and control.
1] ethylene for 48 hours induced abscission of 100% of leaves during treatment, but did not induce any fruit abscission (data not shown).
The 1-MCP treated plants had the lowest rate of leaf abscission during post production shelf life, and after 18 days, only 22% of leaves had dropped, while control plants showed up to 50% of abscission (Figure 1).
The high positive correlation between flowers and harvestable pods confirms the low rate of abscission of these important structures, which determine agronomic yield in mungbean.