Effect of Drought Stress during Grain Filling on Yield and Its Components, Gas Exchange Variables, and Some Physiological Traits of Wheat Cultivars

Abstract

Terminal drought stress during grain filling period has recently become more common in the semiarid Mediterranean regions, where wheat ( Triticum aestivum L.) is grown as an important winter cereal crop. The objective of this experiment was to study the effect of terminal drought stress on grain yield, gas exchang e variables, and some physiological traits of nine bread wheat cultivars. An experiment was carried out in a split-plot arrangement using randomized complete blocks design with three replications during the 2010-2011 season at the research farm of Razi Unive rsity, Iran. Based on the results obtained, post anthesis water deficit significantly decreased grain yield, biomass, 1,000 grain weight, and harvest index of wheat cultivars. Under terminal drought stress and control treatments, there were significant differen ces between cultivars in terms of all traits studied. Also, terminal drought stress decre ased leaf net photosynthesis rate (P n ), stomatal conductance (g s ), transpiration rate, Chlorophyll a, b, and a/b, a nd increased leaf temperature and sub-stomatal CO 2 concentration. Cultivars differed in their response to water stress. In general, tolerant cult ivars showed a higher P n and g s and leaf water content under both moisture conditions compar ed with susceptible ones. A greater reduction in g s and transpiration rate and smaller reduction in P n under stress condition led to a remarkably higher photosynthetic water use efficiency of the tolerant cultivars. Finally, it can be concluded that planting wheat va riety DN-11 in areas with post-anthesis water stress was recommendable for maximizing grain yield. Keywords : Photosynthesis, Relative water content, Stress su sceptibility index, Water use efficiency