Gibberellin-induced inhibition and promotion of sprouting in aerial tubers of Begonia evansiana Andr. in relation to photoperiodic treatment and tuber stage.

Gibberellic-acid (GA3) treatment, when applied within a period ranging from the start of short-day (SD) treatment until about 10 SD, GA3 strongly inhibited formation of aerial tubers in response to SD and brought about sprouting of developing aerial tubers. In contrast, when applied after about 10 SD or more, GA3 hastened the completion of the dormant state in the tubers and prolonged their dormancy. The dormancy-promoting effect of GA3 on detached tubers increased with their degree of maturation. Application of growth retardants N-dimethylaminosuccinamic acid (B-9), 2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine carboxylate methyl chloride (AMO-1618) and 2-chloroethyltrimethylammonium chloride (CCC) to the cuttings delayed the onset of dormancy in the aerial tuber. When the retardants were applied to detached aerial tubers, however, such a delay of dormancy was not observed, and GA3 application did not inhibit sprouting in aerial tubers detached from CCC-treated cuttings.