Effect of 28-homobrassinolide on the performance of sensitive and resistant varieties of Vigna radiata.

A study was undertaken to examine the morpho-physiological alterations under different concentrations of 28-homobrassinolide (HBL) in two contrasting varieties of Vigna radiata. Sterilized seeds of V. radiata (T-44 and PDM-139) were inoculated with specific Rhizobium and allowed to grow and then 14 day old seedlings were exposed to different concentrations (0, 10(-10), 10(-8), or 10(-6) M) of HBL and allowed to grow under natural environmental conditions. At the 15 and 21 day stage, plants were harvested to evaluate various parameters. Results clearly indicated that growth bio-markers, accumulation of proline and activities of various antioxidant enzymes increased significantly in T-44 at a later stage of growth in the presence of HBL whereas, 10(-8) M showed the most promising response. It is concluded that HBL modifies the physiological functions and biochemical metabolism of V. radiata by increasing photosynthetic efficiency at an early stage of growth and antioxidant system in T-44 at a later stage of plant growth that are manifested in growth at later stages. It is believed that increased accumulation of proline and enhanced antioxidant system provide strength to the plants to withstand environmental cues.