Antioxidant Defense in Sunflower against Drought

The sunflower has a fundamental role in the global economy, being one of the most important crops for oil production. The plants have a short growing season and it adapts well to different soil conditions and unfavorable weather. The present study aimed to evaluate the impact of drought on leaf water potential, the content of photosynthetic pigments and antioxidant responses in two cultivars of sunflower. Seeds of the M735 cv. and MG2 cv. were sown in pots and four plants were maintained per pot that was arranged randomly. Plants were grown in a greenhouse, and two months after sowing, subjected to water stress: Irrigated and not irrigated. Evaluations were performed after 1, 5 and 12 days of induction the stress treatment. Significant reduction in leaf water potential at 5 and 12 days in M735 cv. and 12 days for MG2 cv., were observed. The pigment content did not differ between treatments. There was no change in antioxidant enzyme activity for the M735 cv., though the levels of H2O2 increased in non-irrigated plants after 12 days. The SOD and CAT activities increased in the MG2 cv. as a function of water deficit at five and 12 days of water stress. In MG2 cv. was also observed increased levels of H2O2 and lipid peroxidation after 12 days of drought. These results suggest that the major effect of water stress can vary with sunflower cultivars.