Abstract: This paper studied the dynamics of microbial flora and enzyme activity in the rhizosphere of allelopathic rice PI312777 (PI) and nonallelopathic rice Lemont (LE) at the growth stage of 3～7 leaves. The results showed that in the rhizosphere of PI, the amounts of bacteria, actinomycetes and azotobacter were 11.2%～28.3%，40%～78.6% and 111.5%～173.9%, respectively, while that of fungi was lower, with the maximum being 25.5% of that in the rhizosphere of LE, suggesting that allelopathic rice PI promoted the growth of bacteria, actinomycetes and azotobacter, but inhibited that of fungi. Further analysis on the physiological groups of microbial flora showed that PI favored the growth of ammonifier, aerobic azotobacter, aerobic cellulose- decomposer, sulphate- reducer, nitrite- bacteria and nitrate- bacteria, among which, ammonifier and aerobic azotobacter increased by 53.7% and 57.6%, respectively, while inhibited the growth of desulphate bacteria and denitrifyier. Moreover, PI increased the activities of urease, phosphatase and sucrase, but decreased the catalase activity in its rhizosphere.

Key words: Plutella xylostella, critical thermal maximum (CTMax), thermal tolerance, dynamic heating, heating rate