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 ?
The percentage of thinning was determined on two marked branches per plant by counting the fruits present on the day of application and the fruits remaining 15 days after the application of Ethephon in 2009, 2010 and 2011 when the abscission of fruits was complete.
3) Petals showing abscission without any visible signs of wilting and abscission is generally stimulated by exogenous ethylene, e.
Effect of kinetin and chlormequat chloride on growth, leaf abscission and essential oil yield in Mentha arvensis.
seed abscission, and seed germination of Ginkgo in cultivation; (2)
Each stand was then carefully inspected for flower bud damage such as browning/drying of stipules, leaf or flower buds and abscission [16].
Abscission and ethylene production of mango (Mangifera indica L.
onset of flooding, with chlorosis, epinasty, and abscission, and results
These materials are required for building plant structure or preventing the abscission layer formation and consequently, the reduction in pre-harvest fruit dropping [26].
Responses of woody plants to flooding include senescence, shoot dieback, premature leaf abscission, decreased cambial growth, suppression of formation and expansion of leaves and internodes, and reduced photosynthesis and stomatal conductance (Kozlowski 1997).
The number of shoots formed, leaf abscission and cutting mortality was determined by direct count, while two cuttings each were uprooted weekly for the determination of rooting percentage, number of roots per rooted cuttings and mean root length.
There was more leaf necrosis and abscission as well as greater growth inhibition under the high-humidity regime (Norby & Kozlowski, 1982).