Influence of shading on net photosynthetic and transpiration rates, stomatal diffusive resistance, nitrate reductase and biomass productivity of a woody legume tree species (Erythrina variegata Lam.)

Abstract

In view of the sun and shade adaptations of plants to semi-arid climatic conditions investigations were undertaken withErythrina variegata Lam. The studies revealed that shading decreased root and shoot growth, leaf density, leaf area, specific leaf weight, relative growth rate and relative leaf growth rate. Consequently the dry biomass accumulation was adversely affected in shade grown plants. Synthesis of chlorophyll including Chla and Chlb were promoted in the shade grown plants, so as to trap the available sun energy efficiently under shade condition. The Chla/b ratio was decreased in shade grown plants as compared to sun plants. Total soluble protein was reduced, which could be related to the lowered net photosynthetic rate. Thein vivo nitrate reductase (EC 1·6·6·1) activity, an indicator of nitrate utilization was also significantly reduced. Both reduced enzyme activity and net photosynthetic rate could be attributed to the lowered whole plant biomass productivity. The increased stomatal diffusive resistance in shade plants, is associated with the low rate of transpiration. It is concluded that the biomass productivity ofErythrina variegata Lam. under shade condition is drastically reduced by low irradiance.