Root cell elongation inhibition

The hormonal regulation of root elongation in the intact plant is poorly understood. This is partly because all the major plant hormones can inhibit root cell elongation at physiological concentrations. Since roots produce or at least contain each of these inhibitors , it seems clear that root elongation must... 

The kinetics of inhibition of coleoptile cell elongation by supraoptimal concentrations of auxin also differ from the kinetics of inhibition of root cell elongation. In coleoptiles the initial effect of supraoptimal auxin is to promote cell elongation. This is followed by inhibition. In roots the initial effect of high concentrations of auxin is to inhibit elongation (McBride and Evans 1977). 

Caspar et al. (1972) suggested that the inhibition of root elongation by lAA may be caused by a metabolite of lAA, most probably 3-methyleneoxindole (3-MO). However, it has since been shown that purified 3-MO does not inhibit root elongation (Evans 1976c). These data in conjunction with the rapidity (15-20 min) with which intact root growth is inhibited by low concentrations of lAA, indicate that auxin inhibition of root cell elongation is a direct effect. 

Inhibits cell elongation. Also influences developmental cycle, leading to increased flowering and harvest. May also increase chlorophyll formation and root development Animals. 97% is eliminated within 24 hr, principally unchanged Plants. Converted to choline chloride Soil. Rapidly degraded by microbial activity. DTJ0 in 4 soils averaged 32 days at 10°C 1-28 days at 22°C. Low to medium mobility... 

Auxin-like responses, exudates, and initiation of adventitious roots affected. Cell elongation and division promoted or inhibited. Geotropic response lost. 

Root elongation inhibited. Roots swollen, necrotic, collapsed, cells multinucleate. 

The most rapidly growing parts of the plant contain the greatest concentrations of lAA - in the tip of the coleoptile, in buds and in the tips of leaves and roots (24). The concentration of auxin drops from the tip of the coleoptile to the base. From the base of the coleoptile the concentration of auxin increases until it reaches a peak at the root tip. The amount of auxin in the shoot tip, however, is usually much greater than in the tip of the root. In fact, the concentration of auxin which promotes cellular elongation in the shoot appears to be too great for the root, and somehow results in actual inhibition of cell elongation in the root (25). 

In contrast to the auxins and gibberellins, abscisic acid (ABA) and ethylene usually retard cell elongation. With some exceptions (Takahashi 1972, Gaither et al. 1975, Malik and Mehan 1975 a, Van Staden and Bornman 1970) ABA is inhibitory to growth (Addicott and Lyon 1969, Milborrow 1974). ABA inhibits stem and root elongation and counteracts the promotive effects of other substances on these organs (Rehm and Cline 1973, Kaufman and Jones 1974,... 

The effect of GA on root elongation shows some light dependence. Bur-STROM (1960) reported that GA reverses the inhibition of wheat root elongation by light while, in the dark, GA acts to inhibit root elongation, apparently by shortening the cell elongation phase of development. 

Thiocarbamate herbicides, which are normally applied preemergence, exert their herbicidal action at early stages of seedling growth. Grass and some broadleaf weeds are selectively controlled in com, cotton, soybean, and other crops, shoots being more sensitive than roots. In addition, a primary effect of these herbicides appears to be due to inhibition of cell elongation rather than cell division. ... 

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