EFFECT OF -SOLANINE, -CHACONINE AND SOLANIDINE ON THE GROWTH OF IN VITRO CULTURED POTATO (Solanum tuberosum) L. SEEDLINGS

Naturally occurring potato glycoalkaloids are produced mainly in meristematic tissues; an accumulation of these compounds may be observed particularly in response to some adverse conditions such as heat; previous preliminary observations in this respect seem to indicate a possible growth modulating effect by glycoalkaloids in the potato plant. Here we report the results from a series of experiments designed to describe the effect of potato glycoalkaloids in the rooting media on the growth of seedlings developed from axillary buds cultivated in vitro. Axillary buds were obtained from greenhouse plants to study the effect of alkaloids on their growth at ambient and supra optimal temperature. a-Solanine, a-chaconine and solanidine were extracted from meristems and purified by thin layer chromatography; they were found to occur consistently in a ratio of 45:45:10, respectively. Either in these or in equimolar proportions, the isolated alkaloids were mixed and added to the growth medium in order to evaluate their effect on seedling growth. At ambient temperature, when alkaloids were present in the 45:45:10 ratio, results showed a clear negative effect on stem elongation in an concentration dependent fashion; 10uM caused a 48% reduction in stem length with respect to controls after incubation for 45 days; 50 uM further inhibited elongation, caused chlorosis and inhibition of root growth. 100uM caused complete inhibition of seedling development over the same period. Present in equimolar proportion alkaloids did not have as severe an effect. The presence of 50uM total alkaloids in equimolar proportions at 30º C caused a dramatic alteration in developmental pattern resulting in rosette seedlings. A regulatory capacity of alkaloids is discussed.