Changes in morphological and physiological characteristics of sunflower (Helianthus annuus L.) hybrids in relation to the water deficit stress

Sunflower is one of the most cultivated oil crops in the world. In Middle East environments where water deficit frequently occurs, tolerant cultivars and irrigation are used to overcome environmental constraints due to water scarcity. Since, in the literature, the data on the effect of these techniques on morphological and physiological characteristics of sunflower are scarce and contrasting, the aim of this paper was to evaluate the effect of the water deficit stress on morphological and physiological characteristics of sunflower hybrids in a Middle East environment. For this purpose, four hybrids (Azargol, Alstar, Hysun 33 and Hysun 25) sowed under three water regimes [normal irrigation, mild water deficit stress (WD2) and intense water deficit stress (WD3)] in 2009. The results of this study indicated that the highest and least seed yield in normal irrigation was found on Azargol (3448 kg ha) and Hysun 25 (1688 kg ha), respectively. However, in the mild and intense water stress conditions the seed yield with cultivar Alstar having the highest value (2121 and 829 kg ha, respectively) and Azargol and Hysun 33 had the lowest value (893 and 263 kg ha, respectively). The result of this study indicated that application of WD2 and WD3 caused a decrease in leaf area index (LAI) and total dry weight (TDW) of all sunflower hybrids that are studied in this research.