Comparison on Photosynthetic Characteristics of Different Soybean Varieties

Crop production and photosynthetic characteristics are closely related.To investigate the differences between the photosynthetic characteristics of different soybean varieties,field trails were conducted using 7 semi-determinate and 3 determinate soybean cultivars during 2003-2006 year.The photosynthetic rate(Pn)of different nodes at R1,R4 and R6 stage,diurnal changes of Pn under red-blue light source and natural light source at flowering and podding,and Pn of both sides of leaf at flowering and podding were determined.The results showed that ⅰ)the dynamic changes of Pn during the whole growth period were different among soybean varieties,some varieties had higher Pn in former stage and decreased quickly in latter stage,some behaved otherwise,and there still some varieties had a higher Pn during the whole growth period;ⅱ)The Pn showed a decreasing trend from under the pubescent leaf,and the degree varied with varieties;ⅲ)The Pn of front and opposite side of leaves varied greatly,and the ratio of opposite side to front side was different at different growth stages;ⅳ)Diurnal changes of Pn varied with varieties and environments.Even under the same environment,diurnal changes of photosynthetic rate still varied greatly with varieties.It is conclueded that selectiing of high photosynthetic efficiency soybeanshould take into account of various indicators of photosynthetic characteristics.