Effect of irrigation withholding and foliar potassium application on some physiological characteristics and harvest index of two cultivars and a line of bread wheat

In order to evaluate the effect of irrigation withholding and foliar potassium application on some physiological traits (photosynthesis, cell membrane stability and chlorophyll) and harvest index of wheat (Triticum aestivum L.), an experiment was carried out using a split plot factorial based on a randomized complete blocks design with three replications in 2011-2012 at two locations; Seed and Plant Certification and Registration Research Institute, Karaj and Agricultural and Natural Resources Research Center, Yazd. The experimental treatments were included drought stress at three irrigation regimes; irrigation withheld from ear emergence to physiological maturity; irrigation withheld from grain filling to physiological maturity and normal irrigation, foliar potassium application; without potassium application, 1.5 and 3.0 percent K2SO4 and two wheat cultivars; ‘Marvdasht’, ‘Pishtaz’ and a line ‘WS-82-9’. Results showed that the studied characteristics were significantly reduced by increasing drought stress. High harvest index was observed with ‘WS-82-9’ at Karaj under normal irrigation (32.69 percent) and its lower rate was obtained from ‘Marvdasht’ cultivar at Yazd under severe stress (11.50 percent). Cultivars were different for cell membrane stability and its lower rate was related to ‘Marvdasht’ (35.5 percent). Foliar application at 3.0 percent K2SO4 caused the highest values of studied traits, especially for photosynthesis in drought stress condition in a way that photosynthesis increased 99.1 and 69.7 percent in Yazd and Karaj, respectively. It can be concluded that cultivating the wheat line ‘WS-82-9’ and sprayed with 3.0 percent K2SO4 are effective especially in case of shortage irrigation at the end of plant life cycle.