Abstract
Three soybean cultivars, Ohgon, Tanyou and Enrei were planted under field conditions to investigate the after effect of shading (50% of sun light) on the photosynthetic activity at three period in growth stages, i. e., flowering (shading in 43-68 days after emergence); pod formation (shading in 68-88 days after emergence) and maturity stages (shading in 92-109 days after emergence). The shading brought an increase in the length of petiole and stem except cultivar of Tanyou, but had no effect on the fully developed leaflet area on the first day of shading. The specific leaf area was increased and more at lower leaves than upper leaves by the shading treatment. The shaded plants had a higher value in leaf area per root dry weight as compared with the non-shaded plants. Shading treatment at the flowering stage decreased the net photosynthetic rate under saturated light after shading treatment in cultivars of Enrei and Ohgon. But the shaded leaf with treatment at the pod formation stage, showed similar rates to the control in phytosynthesis under saturated light. Shading at the maturity stage increased photosynthetic rates of leaves positioned on each part of the stem as compared with the non-shaded plants.
