Comparison on Yield and Photosynthesis in Canopy in Modern and Old Soybean Cultivars

The yield and photosynthesis of canopy with ten modern and old soybean cultivars were studied.The results showed that the yield of modern cultivars were obviously higher than old cultivars(P0.01),the yield of modern cultivars mainly were concentrated on upper layers and middle layers,but the middle layers yield of old cultivars was the biggest,the upper layers and lower layers yield was lower and no obvious difference in two layers.Leaf area and leaf area index of modern cultivars was higher than that of old cultivars,but no obvious difference.Leaf net photosynthetic rate of modern cultivars was higher than that of old cultivars,at the same time,leaf net photosynthetic rate in different parts of modern cultivars have little differences,leaf net photosynthesis rate in different canopy of that of old cultivars have biggest the differences,especially,the lower layers leaf net photosynthetic rate was decreased obviously;Because the net photosynthetic rate and leaf area index of modern cultivars was higher than that of old cultivars,the photosynthetic ability of modern cultivars obviously higher than that of old cultivars,especially,the photosynthetic ability in lower layers has significantly improved.