Effect of α-Tomatine on the Response of Wheat Coleoptile Segments to Exogenous Indole-3-acetic Acid

Abstract

A concentration of 10−5 M tomatine had no effect on leakage from, or elongation of, wheat coleoptile segments, but consistently reduced IAA-enhanced extension growth by c. 50 per cent. There was no evidence of chemical interaction between the alkaloid and the auxin in solution, and IAA action was not affected by pre-treatment for up to 3 h with 10−5 M tomatine. Studies with [2-14C]IAA revealed that 10−5 M tomatine did not inhibit uptake of auxin into segments. The effect of pre-treating segments for up to 3 h with IAA could be virtually nullified by 10−5 M tomatine, as could also IAA-induced changes in properties of coleoptile cell walls. Results are discussed in relation to the ability of tomatine to disrupt membrane function and to current hypotheses implicating membranes in the primary action of auxin.