Allelochemical stress produced by the aqueous leachate of Callicarpa acuminata:: effects on roots of bean, maize, and tomato

The in vitro effects of an aqueous leachate (1%) of Callicarpa acuminata Kunth. (Verbenaceae) on radicle growth, protein expression, catalase activity, free radical production and membrane lipid peroxidation in roots of bean, maize, and tomato were examined. Aqueous extract of C. acuminata inhibited the radicle growth of tomato by 47%, but had no effect on root growth of maize and beans. 2D-PAGE and densitometry analysis showed that C. acuminata aqueous leachate modified the expression of various proteins in the roots of all treated plants. In treated bean roots, microsequencing analysis of an 11.3-kDa protein, whose expression was enhanced by leachate treatment, revealed a 99% similarity with subunits of alpha -amylase inhibitor of other beans. A 27.5-kDa protein induced in treated tomato showed 69-95% similarity to glutathione-S -transferases (GST) of other Solanaceae. Spectrophotometric analysis and native gels revealed that catalase activity was increased by 2.2-fold in tomato roots and 1.4-fold in bean roots. No significant changes were observed in treated maize roots. Luminol chemiluminescence levels, a measure of free radicals, increased 3.8-fold in treated tomato roots and 2.1-fold in treated bean roots. Oxidative membrane damage in treated roots was measured by lipid peroxidation rates. In tomato we observed a 2.4-fold increase in peroxidation, however, no effect was observed in maize or beans.