Characterization of a carrot callus line resistant to high concentrations of putrescine

Abstract

A mutant carrot callus line resistant to a high concentration (1 mM) of putrescine has been isolated. A high level of endogenous putrescine, about 13-fold higher than in the controls grown in the absence of putrescine, characterized this resistant mutant. Ornithine-, arginine- and S-adenosylmethionine decarboxylase activities were similar in the resistant line and in the controls by the fifth subculture. The uptake of putrescine when supplied to the medium at high concentration (1 mM), was similar in both the putrescine-treated calli and in the untreated controls. At low concentrations (0.64 μM) however the putrescine absorbed by the resistant calli was less than that absorbed by the controls. Putrescine uptake took place almost always against a concentration gradient and might be due to an active mechanism.