Drought stress is one of the most important yield-reducing factors in crop production. Sunflower, an oilseed crop, is severely affected by abiotic stress. In this study, 2 sunflower cultivars (Musala and Aydın) were evaluated in terms of various biochemical and physiological responses under 2 different polyethylene glycol-mediated drought stress conditions. | Research Article Turk J Bot 36 (2012) 707-714 © TÜBİTAK doi: Antioxidative and physiological responses of two sunflower (Helianthus annuus) cultivars under PEG-mediated drought stress Mehmet Cengiz BALOĞLU1,2, Musa KAVAS1,3,*, Gülsüm AYDIN1,4, Hüseyin Avni ÖKTEM1, Ayşe Meral YÜCEL1 1 Department of Biological Sciences, Middle East Technical University, 06800 Ankara - TURKEY 2 Department of Biology, Kastamonu University, 37100 Kastamonu - TURKEY 3 Department of Biology, Yüzüncü Yıl University, 65080 Van - TURKEY 4 Department of Biology, Selçuk University, 42075 Konya - TURKEY Received: ● Accepted: Abstract: Drought stress is one of the most important yield-reducing factors in crop production. Sunflower, an oilseed crop, is severely affected by abiotic stress. In this study, 2 sunflower cultivars (Musala and Aydın) were evaluated in terms of various biochemical and physiological responses under 2 different polyethylene glycol-mediated drought stress conditions. Stress-determining parameters such as malondialdehyde (MDA), hydrogen peroxide (H2O2), and proline contents were determined. Both cultivars showed similar responses at osmotic potentials of both − and − MPa. Aydın was less affected than Musala under these stress conditions. MDA, H2O2, and proline levels were similar at both − and − MPa osmotic potentials in the 2 different cultivars. The 2 cultivars differed significantly in ascorbate peroxidase and catalase enzyme activities, which were more prominent in Aydın for both stress levels. However, glutathione reductase activity did not appear to be an essential part of the antioxidative system in either of the cultivars. Engineering antioxidative enzyme levels might provide a potential mechanism to cope with drought stress in sunflower. Key words: Helianthus annuus, drought stress, antioxidant enzymes, proline Introduction Sunflower (Helianthus annuus L.) is an important agricultural crop and the main
