Abstract
The faba bean (Vicia faba L.) is an important grain legume world-wide, yet the relationship between light intensity, nodule development, and N2 fixation have 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. faba cultivar ‘Xichang Dabai’ were sown in pots in Xichang, China, in 1986-90. The plants subjected to 50% and 20% shading for 145 days had thinner and taller main stems than the control and less flowers, pods and seeds. Low dry weight of organs and less developed underground parts were recognized. Shading caused a deficiency in supplying photosynthates and subsequently the plants formed fewer nodules and showed early nodule senescence. Total N and total sugar contents in roots, stems and leaves were consistently lower under shading regimes, but the contents in nodules did not change significantly. This indicated that the insufficient photosynthate supply limited both N and C metabolism in shaded plants ad caused lower N accumulation due to a decreased nodule mass and an early nodule senescence.
