Ameliorative mechanisms of sodium chloride stress in Sesbania Sesban (L.) merr.

Salinity leads to primary and secondary stresses which includes membrane damage, metabolic disturbance and osmotic stress. Physiological and biochemical responses are induced in plants to ameliorate such stresses. The objective of this study was to obtain a better understanding on salttolerance mechanism of Sesbania sesban to NaCl. Rate of germination was not affected by the NaCl treatment with 50, 100, 150 and 200 mM. Fresh and dry weights were decreased with increasing NaCl concentration. Greater reduction of chlorophyll b content than chlorophyll a suggested that chlorophyll b is more susceptible to salt stress than chlorophyll a. Accumulation of Na⁺ and Cl^– in the old leaves appears to be part of the mechanism to alleviate the salt toxicity. The higher accumulation of proline with increasing NaCl was found in the roots and shoots. Sesbania was found to have a greater tolerance to NaCl that could resist NaCl up to 200 mM is probably related with its ability to restrict Na⁺ and Cl^– content in roots and translocate higher amount of the ions to shoots. The young and old leaves had a higher constitutive level of SOD, APX, CAT and GR activities with increasing NaCl concentrations. These findings indicated that S. sesban has higher levels of antioxidative enzymes both constitutive and induced resulting in greater resistance to oxidative damage caused by NaCl stress.