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Concept
Abscisic acid
Summary
Abscisic acid (ABA or abscisin II) is a plant hormone. ABA functions in many plant developmental processes, including seed and bud dormancy, the control of organ size and stomatal closure. It is especially important for plants in the response to environmental stresses, including drought, soil salinity, cold tolerance, freezing tolerance, heat stress and heavy metal ion tolerance.
In the 1940s, Torsten Hemberg, while working at the University of Stockholm, found evidence that a positive correlation exists between the rest period and the occurrence of an acidic ether soluble growth inhibitor in potato tubers.
In 1963, abscisic acid was first identified and characterized as a plant hormone by Frederick T. Addicott and Larry A. Davis. They were studying compounds that cause abscission (shedding) of cotton fruits (bolls). Two compounds were isolated and called abscisin I and abscisin II. Abscisin II is presently called abscisic acid (ABA).
ABA was originally believed to be involved in abscission, which is how it received its name. This is now known to be the case only in a small number of plants. ABA-mediated signaling also plays an important part in plant responses to environmental stress and plant pathogens. The plant genes for ABA biosynthesis and sequence of the pathway have been elucidated. ABA is also produced by some plant pathogenic fungi via a biosynthetic route different from ABA biosynthesis in plants.
In preparation for winter, ABA is produced in terminal buds. This slows plant growth and directs leaf primordia to develop scales to protect the dormant buds during the cold season. ABA also inhibits the division of cells in the vascular cambium, adjusting to cold conditions in the winter by suspending primary and secondary growth.
Abscisic acid is also produced in the roots in response to decreased soil water potential (which is associated with dry soil) and other situations in which the plant may be under stress. ABA then translocates to the leaves, where it rapidly alters the osmotic potential of stomatal guard cells, causing them to shrink and stomata to close.
Official source
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Ontological neighbourhood
Related publications (7)
Related concepts (13)
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A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, flower, and fruit collectively form the shoot system. In most leaves, the primary photosynthetic tissue is the palisade mesophyll and is located on the upper side of the blade or lamina of the leaf but in some species, including the mature foliage of Eucalyptus, palisade mesophyll is present on both sides and the leaves are said to be isobilateral.
Gibberellin
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Ground tissue
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