Abstract
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-1) and Hysun 25 (1688 kg ha-1), 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-1, respectively) and Azargol and Hysun 33 had the lowest value (893 and 263 kg ha-1, 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. Key words: Sunflower, morphology, physiology, leaf area index (LAI), water deficit stress.
Highlights
Sunflower (Helianthus annuus L.), with a world production of grain and oil, respectively over 28.5 × 106 and 10.5 × 106 Mg achieved on around 22.6 × 106 ha with a seed yield of 1.3 Mg ha-1 (FAO-STAT Agriculture, 2009), is one of the most important sources of edible oil, widely grown in many countries throughout the world (Perry, 1978)
The ANOVA for the studied traits shows that water stress had significant effect (P ≤ 0.01) on leaf number, plant height, head diameter, harvest index and seed yield of all sunflower hybrids (Table 2)
The decrease in seed yield was more pronounced in intense water deficit stress (WD3, 150 mm cumulative evaporation from evaporation pan Class A) than that in the mild water deficit stress (WD2, 100 mm cumulative evaporation from evaporation pan Class A), which may be due to decrease in some morphologic and physiologic traits (Boyer, 1982)
Summary
Sunflower (Helianthus annuus L.), with a world production of grain and oil, respectively over 28.5 × 106 and 10.5 × 106 Mg achieved on around 22.6 × 106 ha with a seed yield of 1.3 Mg ha-1 (FAO-STAT Agriculture, 2009), is one of the most important sources of edible oil, widely grown in many countries throughout the world (Perry, 1978). Sunflower planted area has increased because of moderate cultivation requirements and high oil yield. The term stress is most often used subjectively and with various meanings.
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