Indian Journal of Agricultural Biochemistry

In the present investigation, the effect of osmotic stress induced by PEG-6000 (−0.5 Mpa and-1.0 Mpa) with and without application of 5 mM and 10 mM concentration of proline and betaine aldehyde on antioxidative defense (SOD, GPX, CAT and APX) was studied in two sorghum varieties RSLG 2332 (drought tolerant) and Phule Revati (drought susceptible). Thirty days old seedlings were subjected to osmotic stress and the leaf samples were analyzed for relative leaf water content, chlorophyll and hydrogen peroxide content, lipid peroxidation rate and profile of antioxidative enzymes. The osmotic stress caused reduction in RLWC and chlorophyll content. The hydrogen peroxide and MDA content was significantly higher in drought susceptible Phule Revati (96.13 and 112.81% and MDA 116.04 and 167.65%) when exposed to-0.5 Mpa and-1.0 Mpa osmotic stress respectively. The stressed seedlings when exogenously supplied with 5 mM proline could retain the RLWC and chlorophyll content and maintain lower MDA levels and reduction of H₂O₂ level. The activity of all antioxidative enzymes increased significantly when compared to activity at-0.5 Mpa and-1.0 Mpa osmotic stresses in presence of 5 mM proline and betaine aldehyde. Higher concentration (10 mM) of both proline and betaine aldehyde exhibited less enhancement in activity profile of SOD, GPX, CAT and APX, respectively. This study revealed that application of 5 mM proline and betaine aldehyde to osmotically stressed sorghum seedling helped to retain RLWC, chlorophyll with increased endogenous level of osmolytes which helped in regulating the ROS level as evident from increased antioxidative profile and lower lipid peroxidation rate.