In order to evaluate the effect of drought stress and potassium foliar application on some physiological indices of three wheat (Triticum aestivum L.) cultivars, an experiment was conducted at Seed and Plant Certification and Registration Research Institute (SPCRI), Karaj, Iran. The experimental factors included three irrigation regimes, control (complete irrigation), mild stress (withholding irrigation at grain filling phase) and severe stress (withholding irrigation at ear emergence phase), potassium foliar application, without foliar application, 1.5% and 3.0% K2O and three wheat cultivars (Marvdasht, Pishtaz and WS-82-9). The experiment was carried out in a split plot factorial design based on randomized complete blocks with three replications. Net photosynthesis, leaf stomatal conductance, transpiration rate were measured at two stages; after ear emergence and grain filling stages. In the first measurement of physiological indices, there were no significant differences between drought stress, potassium foliar application and cultivars or for their interaction. Whereas, in the second measurement, net photosynthesis, stomatal conductance, transpiration rate were significantly decreased by drought stress. Also these traits showed significant increase by increasing potassium foliar application. Pishtaz cultivar was better than other cultivars in net photosynthesis.
