Thirty-day-old plants of mustard (Brassica juncea L.) were sprayed with 10-10, 10-8, or 10-6 M aqueous solution of 28-homobrassinolide (HBR). The HBR-treated plants were healthier than those treated with water and yielded more. Maximum increase over control was found in 60-d-old, 10-8 M-HBR-treated plants in fresh and dry mass per plant, carbonic anhydrase (CA, E.C. 4.2.1.1) activity, and net photosynthetic rate (PN), at harvest in number of pods per plant and seed yield per plant (the respective values were 25, 30, 34, 69, 24, and 29 %). A further increase in the concentration of HBR (10-6 M) did not make any additional impact on the growth and yield. Increased CA activity and PN were correlated with growth and seed yield. and S. Hayat ... [et al.].