Study on Change Rule of photosynthetic rate,photo respiration rate and dark respiration rate of muskmelon leaves during seedling

【Objective】 The study probed into the change rule of leaf photosynthesis and leaf photo respiration and dark respiration with environment.【Method】 photosynthetic rate,leaf photo respiration rate,and dark respiration rate were measured for different leaves at different climate and temperature treatments,and those change rules and coefficients of photo respiration and dark respiration were analyzed for different leaves.【Result】 The results show that,it was single peak style curve in cloudy day and double peak style curve in sunny day for dairy change of leaf photosynthetic rate and photo respiration rate and dark respiration rate.The maximum value of the peak was at AM 10-12 on cloudy day,but the peak's time was different with different leaves on sunny days.The photosynthetic rate value of cotyledon was bigger than the first leaf 12 days after sowing,but then reversed.It was a sin function for the temperature effect on the photosynthesis.The photosynthesis rate valued was zero when temperature was lower than 6.5 ℃ or higher than 46 ℃.The maximum value of photosynthesis was at 28 ℃.Coefficient of leaf photo respiration and dark respiration was 0.16 and 0.20 respectively at 25 ℃.【Conclusion】 Muskmelon seedling leaf photosynthesis,leaf photo respiration and dark respiration changed with leaf age,leaf style and environment,and the changing rules for cotyledon and leaves were different.