Abstract: To understand the physiological mechanisms of temperature stress on the diapause larvae of rice stem borer Chilo suppressalis Walker at physiological and biochemical levels, determinations were made on the contents of water, lipid, total sugar and low molecular mass carbohydrates and the activities of SOD, POD, CAT in the larvae after series temperature stress (STS) and gradient temperature stress (GTS). With the decrease of temperature, the water content in the larvae decreased, and the decrement  below 0 ℃was significantly larger in treatment GTS than in treatment STS. The lipid content in the larvae decreased gradually, but no significant difference was observed between treatments STS and GTS. The total sugar content in the larvae in treatment STS increased after an initial decrease, but that in treatment GTS continued to decline. Four species of low molecular carbohydrates, i.e., rehalose, glucose, glycerol and fructose were detected in the larvae. In treatment STS, the contents of glycose, glycerol and fructose in the larvae decreased after an initial increase, while the  trehalose content was in adverse. In treatment GTS, the trehalose content decreased first and increased then, the glucose and glycerol were in adverse, but the fructose content had little change. In the range from 14 to -14 ℃, the SOD and POD activities in the larvae in treatment STS were significantly lower than those in treatment GTS, but the CAT activity was in adverse. The changes of these indices reflected the physiological responses of C. suppressalisdiapause larvae to different temperature stress.  

Key words: Chilo suppressalis Walker, series temperature stress, gradient temperature stress, diapause.