auxin
aux·in
A0541700 (ôk′sĭn)auxin
(ˈɔːksɪn)aux•in
(ˈɔk sɪn)n.
aux·in
(ôk′sĭn)| Noun | 1. |  auxin - a plant hormone that promotes root formation and bud growth |
| 单词 | auxin | ||||||
| 释义 | auxinaux·inA0541700 (ôk′sĭn)auxin(ˈɔːksɪn)aux•in(ˈɔk sɪn)n. aux·in(ôk′sĭn)
auxinauxin(ôk`sĭn), plant hormone that regulates the amount, type, and direction of plant growth. Auxins include both naturally occurring substances and related synthetic compounds that have similar effects. Auxins are found in all members of the plant kingdom. They are most abundantly produced in growth areas (meristem), e.g., root and shoot tips, but are also produced elsewhere, e.g., in the stems and leaves. The method of dispersal throughout the plant body is not yet fully understood. Auxins affect numerous plant processes, e.g., cell division and elongation, autumnal loss of leaves, and the formation of buds, roots, flowers, and fruit. They are also responsible for many forms of tropismtropism, involuntary response of an organism, or part of an organism, involving orientation toward (positive tropism) or away from (negative tropism) one or more external stimuli. ..... Click the link for more information. . It is known that phototropism is due to the inhibition of auxins by light; the cells on that side of a plant exposed to light do not divide or grow as quickly as those on the shaded side, and thus the plant grows toward the light source. Auxins are widely used commercially to produce more vigorous growth, to promote flowering and fruiting and also root formation in plants not easily propagated by stem cuttings, to retard fruit drop, and to produce seedless varieties (e.g., of tomatoes) by parthenogenetic fruiting. Only minute amounts of auxins occur naturally, and synthetic auxins (e.g., 2,4-D) must be administered in carefully prescribed doses, since excessive concentration produces usually fatal abnormalities. However, different species of plants react to different amounts of auxins, a fact used to advantage as a method of weedweed, common term for any wild plant, particularly an undesired plant, growing in cultivated ground, where it competes with crop plants for soil nutrients and water. In their natural habitat, wildflowers and herbs not only provide beauty but function in many useful ways, e.g. ..... Click the link for more information. control. The principal natural auxin is indoleacetic acid; other common but less frequent plant hormones include the gibberellins, lactones, and kinins. auxin[′ȯk·sən]auxinauxin(awk′sĭn) [Gr. auxe, increase]auxina type of plant growth-regulating substance involved in the growth of cells and several other functions. The most important auxin is indolacetic acid (IAA; see Fig. 194 ), but many other substances have been classified as auxins, using a BIO-ASSAY method developed by Fritz WENT.The effects of auxins depend on their concentration in the plant. They are most concentrated at the shoot tip and least concentrated in the root, except for small amounts at the root tip. The major effects of auxin are summarized below:
AUXIN
auxin
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