Comparison of Net Photosynthetic Rate in Leaves of Soybean with Different Yield Levels

A total of nine soybean (Glycine max (L.) Merr.) cultivars were divided into three yield levels which were planted under the same environmental condition. The net photosynthetic rate was measured by LI-6400 portable photosynthesis system. The chlorophyll content and specific leaf weight were measured with regular methods. The results showed that the specific leaf weight, chlorophyll content and net photosynthetic rate of high yield varieties were higher than those of low yield varieties. The yield had a significantly positive correlation with the net photosynthetic rate. With the improvement of modern technology, the net photosynthetic rate could be measured quickly and exactly. Hence, net photosynthetic rate could be used as an effective index in the selection of high yield soybean.