The photosynthetic performances of plants in summer-sowing soybean(Glycine max(L.)Merll)of two varieties(Early matruing No.7 and early maturing No.14)were studied under field conditions in 1986-1987.The results indicated that the maximum value and average value of net photosynthetic rate were bottom leaves>middle leaves>upper leaves on the main stem of soybean plant.The value of leaf area,functional period of photosynthesis and leaf area duration were middle and upper leaves>top leaves>bottom leaves.The average value of photosynthetic rate of leaves on soybean plant was high in seedling and fl...