Effect of Drought Tension and Foliar Application of Zinc on Some Physiological and Agronomic Traits of Safflower Cultivars

In the present research in order to investigate the effect of foliar application of zinc (Zn) on some physiological and agronomic traits of safflower cultivars under drought tension, an experiment was conducted as a split plot factorial based on randomized complete blocks design with three replications for two years (2016-2018) at the experimental field of Seed and Plant Improvement Research Institute in Karaj. In this experiment, irrigation factor in two levels including complete irrigation and drought tension in the form of irrigation-cut from seed filling stage in the main plots, sub-factors including foliar application of zinc from zinc chelate source at three levels of non-foliar application (control) and foliar application at the rate of 0.6 and 1.2 kilogram per hectare and cultivars including 5 safflower cultivars(Sofeh, Golmehr, Goldasht, Padideh and Parnian) were devided into subplots as the factorial arrangement. The results showed that the interaction of irrigation × cultivar on head temperature, chlorophyll index (spad) and grain yield components, interaction of cultivar ×foliar application of zinc on grain yield components and interaction of irrigation × cultivar × foliar application on grian oil percentage was significant at one percent level.  Foliar application of zinc due to a significant increase in the number of heads per plant and the number of seeds per head increased grain yield by 16.5 percent compared to conditions without the use of zinc in safflower. Also, foliar application of zinc at the rate of 1.2 kilogram per hectare in the grain filling stage had the most positive effect on increasing the grain yield components of safflower cultivars, especially Parnian cultivar. In this investigation, Parnian cultivar due to lower head temperature (28.4 degree centigrade) and higher chlorophyll index (69.1) in terms of number of heads per plant (28.4), number of seeds per head (89.8) and one-thousand grain weight (40.46 gram) had a significant superiority over other studied safflower cultivars under drought tension conditions. According to the obtained results, although the drought tension is causing damage to safflower, but foliar application of zink partially compensated the damage caused by drought tension.