Root elongation gibberellin

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,... 

Adventitious Root Formation. IAA stimulates adventitious root formation in cucumber hypocotyl cuttings (28). On the other hand, BR has either no effect or is slightly inhibitory, while it stimulates hypocotyl elongation. Gibberellin is usually inhibitory. However, it has been reported that in mung bean cuttings, the formation of root primordia was not inhibited (29). 

A more interesting herbicide from the viewpoint of lipid metabolism is (2-chloroethyl)trimethylammonium chloride (CCC), a choline analogue. This compound decreases intemodal elongation, but its effect is completely negated by gibberellin. Effects of CCC last for several weeks, but to some extent it can be converted to choline in the plant (Schneider, 1967), and as such incorporated into PC (Willemot and Belzile, 1970). Tanaka and Tolbert (1966) found that CCC stimulated the partially purified choline kinase from leaves. When [ K2]choline was fed to barley or wheat roots, CCC stimulated incorporation into lipids. These effects were reversed by gibberellin. 

Friedberg SH, Davidson D (1970) Duration of S phase and cell cycles in diploid and tetraploid cells of mixoploid meristems. Exp Cell Res 61 216-218 Fuchs Y, Lieberman M (1968) Effects of kinetin, lAA, and gibberellin on ethylene production, and their interactions in growth of seedlings. Plant Physiol 43 2029-2036 Gaither DH, Lutz DH, Forrence LE (1975) Abscisic acid stimulates elongation of excised pea root tips. Plant Physiol 55 948-949... 

Mertz D (1966) Hormonal control of root growth. Plant Cell Physiol 7 125-135 Metzger JD, Zeevaart JAD (1980) Comparison of the levels of six endogenous gibberellins in roots and shoots of spinach in relation to photoperiod. Plant Physiol 66 679-683 Meyer RF, Boyer JS (1972) Sensitivity of cell division and cell elongation to low water potentials in soybean hypocotyls. Planta 108 77-87 Milborrow BV (1966) The effects of synthetic DL-dormin (abscisin II) on the growth of the oat mesocotyl. Planta 70 155-171... 

Odhnoff C (1963) The effect of gibberellin and phenylboric acid on xylem differentiation and epidermal cell elongation in bean roots. Physiol Plant 16 474-483... 

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