Low light stress (20% of normal sun light) from 30 days after sowing to maturity caused marked reduction in the gravimetric growth of shoot, economic yield and yield attributes, partitioning of biomass (harvest index), contents of total sugars, starch and nucleic acids (RNA and DNA) and the activity of nitrate reductase in the shoot of all the diverse crop species tested under low light condition. Height of plants, contents of chlorophyll b, protein, soluble and total organic nitrogen in the shoots, however, increased markedly under low light stress. Different crop species showed marked variation in their growth, yield and biochemical response to low light stress. Among the species tested, maize, rice and okra showed poor economic yield stability (31–36%) under shade as compared to french bean and groundnut (54–77%). The biological yield stability was apparently higher than economic yield stability under shade regardless of different crops species. Among the biochemical parameters, the stability of nucleic acids and chlorophyll a under low light stress was comparatively higher than those of sugars, starch, nitrogen and chlorophyll b.
