Abstract: To explore the physiological effect of heat stress on pea ( Pisum sativum) , hypocotyl growth , membrane injury, ascorbic acid (AsA) , malondialdehyde (MDA) and the expression of Heat Shock Protein 70 (HSP70) in seedling hypocotyls of three pea varieties (produced inMengzi, Shandong and Taiwan) under different heat treatments were examined. The results showed heat stress at 48℃ resulted in decrease in germination rate of seeds and AsA content of seedling hypocotyls, and increase in membrane injury and MDA content. Longer hypocotyls of pea seedling along with higher level of AsA content, membrane thermostability and lower MDA content were found in the germinated seeds which were acclimated at 37℃ for 1 h before heat stress at 48℃ , comparing with no heat-acllimated germinated seeds (heat stres directly at 48℃ ). Except for the Taiwan pea , heat acclimation at 37℃ for 1 h couldn′t induce the expression of HSP70 in the other two varieties. However, the expression of HSP70 in all three varieties was induced by two other different heat treatments, which one was treated at 37℃ for 1 h followed by 48℃ for 2 h with recovery at 22℃ for 1 h and the other treatment was at 48℃ for 2 h . Furthermore , the expression of HSP70 of Mengzi pea was higher when suffering heat stress after heat acclimation heat stress directly .

Key words: Pea ( Pisum sativum)