Effects of heat stress on leaf morphology and photosynthetic characteristics of twenty Acer palmatum Thunb. cultivars

Twenty Acer palmatum Thunb. cultivars were treated under natural high temperature to study effects of heat stress on leaf morphology,net photosynthetic rate,stomata conductance,intercellular CO2 concentration,transpiration rate,water use efficiency,stomata limitation and correlations among these parameters. Results showed that(1) There existed significant differences in heat resistance among these Acer palmatum cultivars. Cultivars of d1118 and c1116 had the best heat resistance which showed no symptoms of heat injury after treatment while cultivars of y1106,y1107 and x1119 had the least heat tolerance and other cultivars were found fallen in between;(2) After heat stress,most cultivars showed obvious stomata suppression,which values of net photosynthetic rate,stomata conductance and transpiration rate were decreased significantly(P 0. 05) or extremely significantly(P 0. 01) and the water use efficiency was increased significantly(P 0. 05);(3) Cultivar of d1118 showed extremely high temperature adaptability because its net photosynthetic rate,stomata conductance and transpiration rate were significantly increased;(4) Cultivar of j1123 belonged to typical non-stomata limitation with decreased net photosynthetic rate but relatively high stomata conductance and intercellular CO2concentration;(5)Leaf heat injury caused by high temperature showed no significant correlation with photosynthetic parameters,but appeared an obvious negative correlation(P 0. 05) with transpiration rate.