Greenhouse experiments showed that the preemergence herbicide fluchloralin ušed at recommended level inhibited the activities of nitiite reductase, net photosynthetic rate and DCPIP photoreduction but did not cause appreciable reduction in nitráte reductase activity. Prolonged treatment of groundnut cv. TMV-2 with fluchloralin resulted in accumulation of nitrite in leaves whereas statistically significant changes were not found in leaf crude protein and chlorophyll contents and growth of plants during different stages of growth.