This study investigated the mechanisms associated with differential salt tolerance in two contrasting rice genotypes (Pokkali and BRRI 3). Plant growth, leaf chlorophyll, and Na+concentrations were significantly affected in BRRI 3 but not in salt-tolerant Pokkali under salt stress. Further, salinity caused upregulation of two chelators namedOsNAS1(nicotianamine synthase) andOsPCS1(phytochelatin (PC) synthase) along with PC accumulation in roots of Pokkali and BRRI 3, though the expression was more pronounced in Pokkali. It suggests that nicotianamine and PC may chelate excess Na+under salt stress. Furthermore, greater induction ofDREB1A(a transcription factor) in Pokkali suggests thatDREB1Amay have involvement in salt-induced gene expression in rice. In Pokkali, salt stress caused significant increase in catalase, glutathione reductase, and superoxide dismutase activity only in roots along with enhanced production of glutathione, proline, arginine, methionine, cysteine, serine, and lysine in leaves. These results suggest that Pokkali plants possibly have better protection mechanism against salt-induced oxidative damage due to active antioxidant activities and higher accumulation of glutathione and proline. Taken together, our findings will be useful for transgenic and breeding programs for salt tolerance in rice. [ABSTRACT FROM AUTHOR]