Diurnal Variation of Net Photosynthetic Rate of Upland-Rice Leaves and Its Relationship with Its Influencing Factors

Two upland-rice varieties(Te-you13,Upland-rice15)were grown in upland conditions,and photosynthesis characteristics and changes of accumulative product of grains in filling stage were studied.The results were summarized as follows: the curves of diurnal variation in the photosynthetic rate of two upland-rice leaves had two peaks and an obvious midday depression at 12:00,although the average photosynthetic rate of upland-rice15 was higher than Te-you13 in a day;the water use efficiency of upland-rice 15 was higher than Te-you13. Under natural conditions,the net photosynthetic rate was significantly positively correlated with photosynthetic active radiation.transpiration rate and stomata conductance,but the net photosynthetic rate was significantly negatively correlated with intercellular CO2 concentration,and was never significantly correlated with water use efficiency by correlation analysis.Based on the tendency of changes in Pn,Gs and Ci,the midday depression in the upland-rice was speculated to have been controlled by stomatal factors.