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Abscission
 
 
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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
Plant

Plants are Life organisms belonging to the Kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae....
 intentionally drops one or more of its parts, such as a leaf
Leaf

In botany, a leaf is an above-ground plant Organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin, to expose the cells containing chloroplast to light over a broad area, and to allow light to penetrate fully into the tissues....
, fruit
Fruit

The term fruit has different meanings dependent on context, and the term is not synonymous in food preparation and biology. In botany, which is the scientific study of plants, fruits are the ripened Ovary of flowering plants....
, flower
Flower

A flower, sometimes known as a bloom or blossom, is the reproduction structure found in flowering plants . The biological function of a flower is to mediate the union of male sperm with female ovum in order to produce seeds....
 or seed
Seed

A seed is a small Plant embryogenesis plant enclosed in a covering called the seed coat, usually with some Food storage. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant....
, though the term is also used to describe the shedding of a claw
Claw

A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end of the leg or Arthropod leg for gripping a surface as the creature walks....
 by an animal, and is also the word used to describe the separation of daughter cells at the end of cytokinesis
Cytokinesis

Cytokinesis is the process where the cytoplasm of a single eukaryotic cell is divided to form two daughter cells. It usually initiates during the late stages of mitosis, and sometimes meiosis, splitting a binucleate cell in two, to ensure that chromosome number is maintained from one generation to the next....
, a process that generally begins immediately following mitotic telophase
Telophase

Telophase , from the ancient Greek "te???" and "fas??" , is a stage in either meiosis or mitosis in a eukaryote cell reversing the effects of prophase and prometaphase events....
.

ant will abscise a part either to discard a member that is no longer necessary, such as a leaf during autumn, or a flower following fertilisation
Fertilisation

Fertilisation , is the fusion of gametes to produce a new organism. In animals, the process involves a sperm fusing with an ovum, which eventually leads to the development of an embryo....
, or for the purposes of reproduction.






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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
Plant

Plants are Life organisms belonging to the Kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae....
 intentionally drops one or more of its parts, such as a leaf
Leaf

In botany, a leaf is an above-ground plant Organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin, to expose the cells containing chloroplast to light over a broad area, and to allow light to penetrate fully into the tissues....
, fruit
Fruit

The term fruit has different meanings dependent on context, and the term is not synonymous in food preparation and biology. In botany, which is the scientific study of plants, fruits are the ripened Ovary of flowering plants....
, flower
Flower

A flower, sometimes known as a bloom or blossom, is the reproduction structure found in flowering plants . The biological function of a flower is to mediate the union of male sperm with female ovum in order to produce seeds....
 or seed
Seed

A seed is a small Plant embryogenesis plant enclosed in a covering called the seed coat, usually with some Food storage. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant....
, though the term is also used to describe the shedding of a claw
Claw

A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end of the leg or Arthropod leg for gripping a surface as the creature walks....
 by an animal, and is also the word used to describe the separation of daughter cells at the end of cytokinesis
Cytokinesis

Cytokinesis is the process where the cytoplasm of a single eukaryotic cell is divided to form two daughter cells. It usually initiates during the late stages of mitosis, and sometimes meiosis, splitting a binucleate cell in two, to ensure that chromosome number is maintained from one generation to the next....
, a process that generally begins immediately following mitotic telophase
Telophase

Telophase , from the ancient Greek "te???" and "fas??" , is a stage in either meiosis or mitosis in a eukaryote cell reversing the effects of prophase and prometaphase events....
.

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 following fertilisation
Fertilisation

Fertilisation , is the fusion of gametes to produce a new organism. In animals, the process involves a sperm fusing with an ovum, which eventually leads to the development of an embryo....
, or for the purposes of reproduction. Most deciduous
Deciduous

Deciduous means falling off at maturity or tending to fall off and is typically used in reference to trees or shrubs that lose their leaves seasonally and to the shedding of other plant structures such as petals after flowering or fruit when ripe....
 plants drop their leaves by abscission before winter, while evergreen
Evergreen

In botany, an evergreen plant is a plant having leaf all year round. This contrasts with deciduous plants, which completely lose their foliage for part of the year....
 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 conserve water
Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
 or photosynthetic efficiency, depending on the 'costs' to the plant as a whole. The abscission layer is a greenish grayish color.

Types

In deciduous
Deciduous

Deciduous means falling off at maturity or tending to fall off and is typically used in reference to trees or shrubs that lose their leaves seasonally and to the shedding of other plant structures such as petals after flowering or fruit when ripe....
 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
Woody plant

A woody plant is a Vascular tissue plant that has a Perennial plant Plant stem that is above ground and covered by a layer of thickened bark. Woody plants are adapted to survive from one year to the next; the stem supports continued vegetative growth above ground from one year to next....
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 to decay
Decay

Decay may refer to:*Decay , a comic book character*Decay , a french musicband*Bacterial decay, decomposition of organic matter*Radioactive decay...
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
Ethylene

Ethylene is the chemical compound with the formula C2H4. It is the simplest alkene. Because it contains a carbon-carbon double bond, ethylene is called an unsaturated hydrocarbon or an olefin....
 can stimulate abscission. While researchers originally believed abscisic acid
Abscisic acid

Abscisic acid , also known as abscisin II and dormin, is a plant hormone. It functions in many plant developmental processes, including bud dormancy....
 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.

Auxin
Auxin

Auxins are a class of plant growth substance . Auxins play an essential role in coordination of many growth and behavioral processes in the plant life cycle, they and the behavior they played in plant growth was first revealed by a Dutch scientist named Fritz Went ....
 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.

See also

  • Marcescence
    Marcescence

    Marcescence is the retention of dead plant organs that normally are shed. It is most obvious in deciduous trees that retain leaves through the winter....
    , the retention of normally shed plant parts


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