AbstractThe faba bean (Vicia fabaL.) is an important grain legume world wide, yet the relationship between light intensity and nodule development and N2fixation has received minimal attention. An experiment was conducted to study the effects of shading on faba bean growth, seed yield, nodule development, and the distribution of total N and total sugar among plant parts. Seeds of the V.fabacultivarXichang Dabaiwere sown in pots at Xichang. China, in 1986–90. The plants subjected to 50 and 20 shading for 145 d had thinner and taller main stem than the control, and fewer flowers, pods, and seeds. Poor dry weight of organs and less developed underground parts were recognized. Shading caused the deficiency of photosynthate (supply), subsequently less nodules formed poorer fresh weight of nodules was produced and nodule senescing advanced. Total N and total sugar contents per plant and in roots, stems and leaves were consistently lower under shading regimes, but the contents in nodules did not change significantly. It seems that the insufficient photosynthate supply limited both N and C metabolism in shading plants by first limiting growth of the whole plant and nodule, and that the lower total N content in faba bean plant under shading regime was attributed to an decreased effective nodule mass and advanced nodule senescin
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