Effect of abscisic acid and chlorocholine chloride on nodulation and biochemical content of Vigna radiata L. under water stress

The present study was carried out to evaluate the effect of abscisic acid (ABA) and chlorocholine chloride (CCC) on growth, nodulation and changes in endogenous level of plant hormones indole acetic acid (IAA) and Gibberellic acid (GA) of mung bean grown under normal or water stress conditions. Two varieties (cv. NM-98 and cv. HCM-209) of mung bean were soaked in 10-6 M ABA or in chlorocholine chloride and grown for five weeks under non-stress conditions after which water stress was imposed at 50% flowering (37 days after sowing). Drought stress reduced fresh and dry weight of root and shoot, decreased the diameter of pink bacteroid tissue and number of root nodules. However, ABA and CCC pre- soaking treatments partially alleviated the inhibitory effect of drought. Pre- soaking with ABA or CCC in non-stressed or stressed plants caused increase in proline, protein, sugar and chlorophyll content and peroxidase activity of leaves. However, ABA tr eatment caused a maximal increase in proline accumulation while maximal increase in peroxidase activity was observed in plants raised from seeds treated with CCC. Likewise, endogenous levels of phytohormones GA and lAA were also increased following ABA application whereas, CCC increased IAA. Maintenance of water budget by increase in relative water content of leaves, greater increase in proline production, higher activity of antioxidant enzyme, peroxidase and better survival of Rhizobium in soil following ABA and CCC application appears to be the mechanism for providing mung bean tolerance to water stress. The effects of CCC was similar to ABA under water stress and may be implicated to combat water stress on farmers level because of better cost benefit ratio as compared to ABA.