Effect of exogenous application of plant growth regulators on quantitative and qualitative of grain yield and gas exchange rate of different bread wheat cultivars

Plant growth regulators are the most important factors that regulate crop production. Hence, this study was conducted to evaluate the effect of some plant growth regulators on physiological traits, gas exchange variables and grain yield quality and quantity of wheat in Razi university, Iran, in 2013-2014 crop year. A factorial experiment based on randomized complete block design (RCBD) with three replications was used. In this study, the first factor included 10 bread wheat cultivars (Zare, Parsi, Sivand, Pishtaz, Bahar, Azar 2, Bezostaya, Gaspard, Sirvan, and Marvdasht) and also the second factor at four levels included foliar application of 50 μM concentration of cytokinin, auxin, gibberellin and lack of foliar application (control) at flowering and booting stages of the spike. The results showed that there were significant differences among cultivars in terms of agronomic and physiological traits. Sivand and Parsi cultivars had the highest grain yield, biological yield, harvest index, number of grains per spike, thousand grain weight, hectoliter weight, photosynthetic rate and chlorophyll a, but Azar 2 cultivar had the lowest of the above traits. The results showed that application of plant growth regulators increased grain yield, biological yield, harvest index, thousand grain weight, photosynthesis rate, soluble proteins content and crude protein. Among the investigated plant growth regulators, the application of 50 μM of cytokinin caused the highest increase in the rate of plant photosynthesis (18.4%).