Abstract:In order to identify the thermotolerance of Luffa acutangula,thirty-two varieties were screened,and the physiological response to heat stress with different heat resistance,such as WB121(tolerant),WB105(susceptible) and YL8(intermediate),was studied.The results showed that 32 luffa varieties included 3 heat-tolerant,4 heat-susceptible,and 25 intermediate varieties.The relative conductivity (RC),the contents of malondialdehyde (MDA) and soluble sugar (SC) in three varieties gradually increased with the prolongation of heat stress.However,there is no significant difference in activities of three antioxidases (SOD,CAT and POD) within these cultivars.The chlorophyll fluorescence parameters (Fv/Fm,Yeild and ETR) of all the three luffa varieties decreased with the time of heat stress,in which the susceptible variety WB105 had significant decline.The Pearson correlation analysis indicated that the heat injury index had positive correlation with RC,MDA and SC,but negative with the chlorophyll fluorescence parameters (Fv/Fm,Yeild and ETR),and the correlations between the heat injury index and three antioxidases (SOD,CAT and POD) activities were not significant.Therefore,the chlorophyll fluorescence parameters (Fv/Fm,Yeild and ETR) are rapid and accurate indicator of the heat injury and could serve as important physiological parameters for identification of thermotolrance in Luffa acutangula at the seedling stage.