The effect of 30 % defoliation of shaded leaves in lower layers of plant was studied on activities of carbonic anhydrase (CA) and ribulose-1,5-bisphosphate carboxylase (RuBPC), leaf dry mass per unit leaf area, and plant dry mass of mustard (Brassica juncea). Removal of 30 % of leaves resulted in increased CA and RuBPC activities of leaves, and leaf and plant dry masses.