LAUSR

The present study investigated different levels (S1: 100% of field capacity- Control S2: 50% of field capacity-moderate stress; S3: 0% of field capacity-severe stress) of drought stress on oxidative damages and variations in antioxidants in the two bean varieties Bn-16 (drought-sensitive), Bn-150 (drought-tolerant) to elucidate the antioxidative protective mechanism governing differential drought tolerance. The shoot fresh weight, shoot height, leaf number and area, RWC were reduced with different level of drought stress. However this reduction clearly occurred in Bn-16 (sensitive). Antioxidative enzyme activities, such as superoxide dismutase, catalase, ascorbate peroxidase and glutation reductase, had a greater increase in tolerant genotypes (Bn-150) than in sensitive ones (Bn-16). The level of lipid peroxidation was measured by estimating malondialdehyde content. Lipid peroxidation increased with increasing drought conditions in all genotypes, although Bn-150 was the least affected when compared with the other genotype. Total phenolic and flavonoid content increased in bean genotypes under S2 and S3 conditions. The highest total phenolic and flavonoid contents were attained in Bn-150 subjected to S3 treatment. These results indicated that an antioxidant defence system, osmolytes (such as proline), and secondary metabolites play important roles in common bean (Phaseolus vulgaris L) during drought stress and recovery.