Biochemical Studies on Evaluation of Sunflower (Helianthus annuus L.) Genotypes for Heat Stress

Crops are facing heat stress because of rapid climate change caused by global warming. We examined these issues in sunflower by exposing the plants growing with mean maximum temperature of 32.2oC (sowing to flowering) and 36.1oC (flowering to harvest) at normal temperature (S1) and 35.3oC (sowing to flowering) and 38.3 oC (flowering to harvest) at high temperatures (S2) by staggered sowings. Antioxidative responses of sunflower were also explored by studying the Superoxide dismutase, Catalase, Peroxidises and Ascorbate peroxidise activities. A significant increase was observed in antioxidant enzyme activities under high temperature stress. The final oil composition proved to be sensitive to the timing of heat stress and reduced (13%) by high temperatures. Some innovative steps should be taken on an emergency basis to prepare plants for such stressful conditions.