عنوان مقاله [English]
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 in two locations: Seed and Plant Certification and Registration Research Institute, Karaj and Agricultural and Natural Resources Research Center, Yazd. The experimental factors were included drought stress (three levels of irrigation withholdings were 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% K2SO4) and genotype (two wheat cultivars of ‘Marvdasht’, ‘Pishtaz’and aline‘WS-82-9’). Results showed that the studied characteristics were significantly reduced by increasing drought stress level. The highest harvest index was observed in ‘WS-82-9’ in Karaj under normal irrigation (32.69%) and the lowest harvest index was obtained from ‘Marvdasht’cultivarin Yazd, under severe stress (11.50%). Genotypes were different for cell membrane stability and the lowest rate was belonged to ‘Marvdasht’ (35.5%). Foliar application of 3.0% K2SO4 caused to significant differences in physiological characteristics, especially for leaf photosynthesis under severe drought stress condition: photosynthesis increased 99.1 and 69.7% in Yazd and Karaj, respectively. It can be concluded that cultivating of ‘WS-82-9’ and spraying of 3.0% K2SO4 were effective to moderate drought stress, especially when fields have limitations for irrigation water at the end of crop life cycle.