Changes in Acetylcholine-Hydrolyzing Activity in Heat-Stressed Plant Cultivars

Abstract

The differences in the acetylcholine (Ach)-hydrolyzing activity in tessues and the changes in the enzyme activity after heat stress in yard-long bean, cucumber and radish plaants were determined. Specifically a comparison was made between Malaysian cultivars from the tropical zone and Japanese cultivars from the temperate zone. High Ach-hydrolyzing activity was found in the primary and secondary pulvini of yard-long bean, stem and node of cucumber, and petiole and root of radish. After heat stress, a significant increase in the enzyme activity was found in the same organs of three crops. Contrasted with Japanese cultivars, the ACh-hydrolyzing activity of Malaysian cultivars was more than 2 fold higher. Malaysian cultivars were distinguished by their remarkable changes in enzyme activity after heat stress. Furthermore, the ACh-hydrolyzing activity was inhibited 82-95% by neostigmine bromide, an inhibitor of ACh esterase. The results showed ACh-hydrolyzing activity responded to heat stress. Specifically, there were significant changes of enzyme activity in pulvini of yard-long bean, stem and node of cucumber, and petiole and root of radish after heat stress. Especially, the results demonstrated significant changes of enztme activity in Malaysian cultivars after heat stress.