Abstract: The changes of leaf area increase,photosynthetic rate,SPAD values of cucumber leaves and contents of starch,carbohydrate and MDA between functional leaves and old leaves were studied in greenhouse under high temperature and elevated CO₂ coupling. The purpose of research was to investigate the effect of high temperature and elevated CO₂ coupling on photosynthesis and leaf senescence of cucumber in greenhouse. Main results were as follows:Both the net photosynthetic rate and SPAD values increased markedly under high temperature and elevated CO₂ coupling. But the values under high temperature with high concentration of CO₂ reached at the peak level after treatment of 13 days; the values under high temperature with medium concentration of CO₂ were significantly higher than control,high temperature with low concentration CO₂ and high temperature treatments during 10-19 days. Comparing with the functional leaves,contents of starch went up and contents of carbohydrate declined remarkably in old leaves under high temperature with high concentration of CO₂; while there was no significant change in contents of starch and carbohydrate under high temperature with medium and low concentration of CO₂. The content of MDA in old leaves under high temperature with high concentration of CO₂ grew significantly,and it was higher than those in other treatments except in high temperature treatment. The result above illustrated that under high temperature photosynthesis of cucumber would be increased quickly,but the speed of leaf senescence would also grew up with high concentration of CO₂; while photosynthesis of cucumber would be increased continually,and the speed of leaf senescence would be decreased with medium concentration of CO₂.

Key words: Cucumber, High temperature, CO₂ enrichment, Photosynthesis rate, Leaf senescence

CLC Number: 

• S626

• S642.2