INTERACTION OF GIBBERELLIN A3, AND INORGANIC PHOSPHATE IN TOBACCO SEED GERMINATION

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Abstract
Investigation was made on the influence of inorganic phosphate upon the germination of positively photoblastic tobacco seed (Nicotiana tabacum L. var. uirginica (AGDH.) COM. “Bright Yellow”) induced by GA3, GA3M, kinetin, red light, and ammonium salts of various organic acids. Inorganic phosphate increases the GAs-induced germination, and inhibits the germination caused by ammonium citrate, while it does not influence the germination brought about by GA3M, kinetin, and red light. The optimum pH for the GA3-induced germination lies in the acidic pH range, indicating that the undissociated form of GA3 is operative. The stimulatory effect of phosphate is, however, not ascribed merely to the pH control in the mediurr. Phosphate exerts some specific influence for which the presence of the free carboxyl group of GAs is required. The observed contrasting effects of phosphate on the GA3-induced germination (i.e., acceleration), on the one hand, and on the ammonium citrate-induced germination (i.e., inhibition), on the other, were explained by assuming that the phosphate effects ultimately consist in accelerating the uptake of the carboxylic acid into the seeds. GA3M also has an activity of inducing the germination of tobacco seed without light.

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