Effect of 28-homobrassinolide on the nitrate reductase, carbonic anhydrase activities and net photosynthetic rate in Vigna radiata

The foliage of fifteen day-old Vigna radiata seedlings was sprayed with water (control) or with a 10–10 M, 10–8 M or 10–6 M aqueous solution of 28-homobrassinolide (HBR). Samples of the treated plant material, collected at 30/50 days after sowing (DAS), were assessed for the activities of carbonic anhydrase (CA) and nitrate reductase (NR); leaf chlorophyll content (Chl); stomatal conductance (gs); carboxylation efficiency (CE), and net photosynthetic rate (PN). 28-homobrassinolide generated a significant impact on all these characteristics and on seed yield at harvest. Among the treatments, 10–8 M proved best, in which case the values for the above six physiological parameters in 30 days-old plants increased by, respectively, 31, 29, 27, 28, 29 and 33% over the control. Moreover, the harvest weight of the seeds of these plants was 27% larger than in the control.