- Abscission
Abscission (from Latin abscindere, from ab- ‘off, away’ + scindere ‘to cut’) is the shedding of a body part. It most commonly refers to the process by which a
plant intentionally drops one or more of its parts, such as aleaf ,fruit ,flower orseed , though the term is also used to describe the shedding of aclaw by an animal.Use
A plant will abscise a part either to discard a member that is no longer necessary, such as a leaf during
autumn , or a flower followingfertilisation , or for the purposes ofreproduction . Mostdeciduous plants drop their leaves by abscission before winter, whileevergreen plants continuously abscise their leaves. Another form of abscission is fruit drop, when a plant abscises fruit while still immature, in order to conserve resources needed to bring the remaining fruit to maturity. If a leaf is damaged a plant may also abscise it to conservewater orphotosynthetic efficiency, depending on the 'costs' to the plant as a whole. The abscission layer is a greenish grayish color.Types
In
deciduous trees, an abscission zone, also called a separation zone, is formed at the base of the petiole. It is composed of a top layer which has cells with weak walls, and a bottom layer which expands in the autumn, breaking the weak walls of the cells in the top layer. This allows the leaf to be shed.In
woody plant s, an abscission layer is formed composed of parenchyma cells bounded on both sides with cork. This layer is found at the base of the leaf petioles in woody angiosperms and gymnosperms and because of the disintegration of the parenchyma layer, the organ, such as a leaf or bark, is separated from the parent plant. Abscission is a natural process of plant growth induced by the plant, in contrast todecay ing or falling off due to other causes.The liberation of a fungal spore by the withering away of an adjoining layer is also called abscission.
Hormone involvement
The gaseous plant hormone
ethylene can stimulate abscission. While researchers originally believedabscisic acid to be the hormone that stimulated abscission (for which the hormone was named), it was later proven that it does not play a primary role.Fact|date=September 2007Auxin is a plant hormone which can prevent the formation of abscission layers and premature fruit drop. Auxin is also believed to play a part in the shedding of leaves and their autumn color change. This happens due to continuous release of auxin in a young leaf; however, as leaves gets old and auxin supply dwindles, an abscission layer forms and leaves shed. In woody plants preparing to shed their leaves, the abscission zone or layer cuts off the movement of auxin from the leaf blade to the leaf. Fact|date=September 2007ee also
*
Marcescence , the retention of normally shed plant partsExternal links
* [http://www.microscopyu.com/galleries/confocal/abscission.html Absission layer microscopy]
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abscission — ● abscission nom féminin (latin abscissio, de abscindere, couper) Rupture normale du pédoncule des feuilles d automne ou des fruits mûrs, entraînant leur chute. ⇒ABSCISION, ABSCISSION, subst. fém. CHIR., vieilli. Synon. de excision, action de… … Encyclopédie Universelle
Abscission — Ab*scis sion, n. [L. abscissio. See {Abscind}.] 1. The act or process of cutting off. Not to be cured without the abscission of a member. Jer. Taylor. [1913 Webster] 2. The state of being cut off. Sir T. Browne. [1913 Webster] 3. (Rhet.) A figure … The Collaborative International Dictionary of English
abscission — index cancellation Burton s Legal Thesaurus. William C. Burton. 2006 … Law dictionary
abscission — (n.) removal or cutting away, early 15c., from L. abscissionem (nom. abscissio) a cutting off, noun of action from pp. stem of abscindere (see ABSCISSA (Cf. abscissa)) … Etymology dictionary
abscission — [ab sizh′ən] n. [ME abscisioun < L abscissio: see ABSCISSA] 1. a cutting off, as by surgery 2. the normal separation of fruit, leaves, etc. from plants by the development of a thin layer of pithy cells at the base of their stems … English World dictionary
Abscission — Abszission bezeichnet das Abwerfen von Blättern, Früchten und anderen Pflanzenteilen wie Laub und Blütenknospen, Zweigen, Stacheln, Dornen oder Blütenständen. Man spricht daher auch vom Blattfall, Fruchtfall, Laubfall, Knospenfall, Blütenfall.… … Deutsch Wikipedia
abscission — noun Etymology: Middle English abscisioun, from Anglo French abscission, Latin abscission , abscissio, from abscindere Date: 15th century 1. the act or process of cutting off ; removal 2. the natural separation of flowers … New Collegiate Dictionary
Abscission — L abscission est le processus par lequel un fruit ou une feuille se détache de l arbre (s effeuille). Elle dépend de l équilibre entre plusieurs régulateurs de croissance aux effets antagoniste. L auxine et les brassinostéroïdes ont un effet… … Wikipédia en Français
abscission — /ab sizh euhn, sish /, n. 1. the act of cutting off; sudden termination. 2. Bot. the normal separation of flowers, fruit, and leaves from plants. [1605 15; < L abscission (s. of abscissio). See ABSCISSA, ION] * * * … Universalium
abscission — noun a) The act or process of cutting off. Not to be cured without the abscission of a member. b) The state of being cut off. See Also: abscise, abscisic, abscisic acid, abscisin, abscissin … Wiktionary