The Role of Calcium in the Response of Roots to Auxin and Gravity
There is growing interest in the possibility that calcium (Ca) serves as a second messenger in the response of plant cells to hormones and environmental stimuli [5, 11, 22]. Some studies indicate that cytoplasmic Ca levels in plant cells may be controlled by the inositol trisphosphate pathway in much the same manner as in animal cells . Schumaker and Sze  reported that IP3 (inositol 1,4,5-trisphosphate) induces Ca release from vacuolar membrane vesicles and that this effect is blocked by TMB-8 [8-(N,N-dimethylamino)-octyl 3,4,5-trimethoxybenzoate-HCl], an antagonist of intracellular Ca release (also see references cited in ). Recent evidence indicates that hormonal promotion of cell elongation and perhaps cell wall biosynthesis may be mediated by changes in cytoplasmic Ca levels. Some of these effects may depend upon activation of calmodulin. (CaM) by Ca since CaM antagonists interfere with auxin-induced cell elongation [3, 23]. Brummell and Maclachlan  have found that TMB-8 inhibits both auxin-induced growth and auxin-induced wall biosynthesis in pea stem segments and they noted that Ca could restore auxin-induced enhancement of wall biosynthesis in segments treated with TMB-8.
KeywordsMaize Agar CaCl Mannitol Inositol
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