Exogenously applied ABA induced changes in physio-biochemical attributes in selected rice varieties under osmotic stress

Drought is the most catastrophic abiotic stress that affect plant growth and development. Plant initiates alterations at physiological, biochemical and molecular levels to combat deleterious effects of drought in which abscisic acid, play a pivotal role. The present investigation was conducted to investigate how abscisic acid modulates different biochemical traits under osmotic stress. Twenty-one days old seedlings were exposed to osmotic stress, exogenously applied abscisic acid and the combination of both osmotic stress and abscisic acid to study the influence of abscisic acid on biochemical traits under moisture stress. The results reveals that abscisic acid has no influence on leaf water potential, however, it has active role in increasing osmolytes like proline. {Delta}1-pyrroline-5-carboxylate reductase and proline dehydrogenase remained unresponsiveness to ABA that indicates ABA-independent regulation of these two enzymes but the activity of {Delta}1-pyrroline-5-carboxylate synthesase and Ornithine-{delta}-aminotransferase was enhanced (3 fold) in response to abscisic acid. Antioxidative enzymes increased (catalase-2.5 fold; peroxidase-3 fold and SOD-6 fold) in response to abscisic acid and osmotic stress, gave an insight of the regulation of these traits under the influence of abscisic acid. Aldehyde oxidase remained unresponsive to abscisic acid but showed enhanced expression when both abscisic acid and osmotic stress was applied suggest its ABA-independent regulation. The information provided here has significance in understanding the regulation of different catabolite that play important role in drought tolerance and can be implemented for the development of drought-tolerant varieties.