Drought induced physiological and biochemical responses in Solanum lycopersicum genotypes differing to tolerance

Drought stress is one of the most serious abiotic stresses that cause reduction in plant growth, development and yield in many parts of the world. The plants have developed different morphological, physiological and biochemical mechanisms to withstand drought stress. The present study investigated different levels (S1: 100% of field capacity – Control; S2: 50% of field capacity –moderate stress; S3: 0% of field capacitysevere stress) of drought stress on oxidative damages and variations in antioxidants in the two tomato genotypes Tom-163 (drought-sensitive), Tom-143 (drought-tolerant) to elucidate the antioxidative protective mechanism governing differential drought tolerance. The shoot fresh weight, shoot height, leaf number and area, relative water content (RWC) were reduced with different level of drought stress. However, this reduction clearly occurred in Tom-163 (sensitive). Antioxidative enzyme activities such as superoxide dismutase, catalase, ascorbate peroxidase and glutation reductase had a greater increase in tolerant genotypes (Tom-143) than in sensitive ones (Tom-163). The level of lipid peroxidation was measured by estimating malondialdehyde content. Lipid peroxidation increased with rising drought level in both genotypes although Tom-143 was the least affected when compared with the Tom-163. Total phenolic and flavonoid contents increased in tomato genotypes under S2 and S3 conditions. The highest total phenolic and flavonoid contents were attained in Tom-143 subjected to S3 treatment. These results indicated that antioxidant defense systems, osmolytes and secondary metabolites play important roles in tomato during drought stress.