auxin
auxin A hormone that promotes longitudinal growth in the cells of higher plants. Typically, low concentrations of auxin promote growth whereas high concentrations inhibit it. Auxins are produced at the growing points of stems and roots, and promote growth by increasing the rate of cell elongation rather than that of cell division. They are involved in the curvature of parts of the plant towards light (phototropism) or gravity (geotropism), and the initiation of cambium activity in association with cytokinins; and they may control fruit growth or leaf fall, and inhibition of lateral-bud development in favour of apical buds. A natural example of an auxin is indole-3-acetic acid (IAA), which has been isolated from fungi and bacteria, and from the endosperm of corn, as well as from urine and saliva in humans. Auxins have also been synthesized, and are widely used to regulate growth in a variety of plants of agricultural and horticultural importance. Some of these may have differential effects on different plants. For example 2, 4-dichlorophenoxyacetic acid (2, 4-D) is toxic to dicotyledons (see DICOTYLEDONEAE) but not to monocotyledons (see MONOCOTYLEDONEAE), and is used to control weeds in cereal crops and lawns.
auxin
auxin Any of a group of plant growth substances responsible for such processes as the promotion of growth by cell enlargement, the maintenance of apical dominance, and the initiation of root formation in cuttings. Auxins are also involved in suppressing the abscission of leaves, fruit, or other plant organs and in the development of flowers and fruits. Naturally occurring auxins, principally indoleacetic acid (IAA), are synthesized in actively growing regions of the plant, from where they are transported to other parts of the plant. IAA is stored in the plant in an inactive form, conjugated (attached) to various compounds, such as myo-inositol. Synthetic auxins include 2,4-D, which is used as a weedkiller, and indolebutyric acid and naphthaleneacetic acid, which are sold in preparations of ‘rooting hormones’.
auxin
auxin Plant hormone produced mainly in the growing tips of plant stems. Auxins accelerate plant growth by stimulating cell division and enlargement, and by interacting with other hormones. Actions include the elongation of cells in geotropism and phototropism (by increasing the elasticity of cell walls, allowing the cells to take up more water), fruit drop and leaf fall. See also gibberellin
More From encyclopedia.com
Gibberellins , gibberellin The generic name of a group of plant hormones that stimulate the growth of leaves and shoots. Unlike auxins, they tend to affect the whol… kinetin , cytokinin (kinin) Any of a group of plant growth substances chemically related to the purine adenine. Cytokinins are involved in numerous aspects of… Tropism , Unlike animals, plants cannot move to more favorable locations. Instead, plants survive by adjusting their growth to their local environment. A major… Plants , Plants
A plant is a multicelled organism that makes its own food by photosynthesis. Although plants show a variety of form, function, and activity, a… Seed , Seed
A seed is a part of a flowering plant involved in reproduction. It consists of three major parts: the embryo, endosperm, and testa. The embryo i… Fertilizer , A fertilizer is a plant nutrient added to a soil to increase its yield. Plants need nutrients to grow and produce fruits and vegetables. Two categori…
You Might Also Like
NEARBY TERMS
auxin