Effects of plant growth regulator on some photosynthesis parameters and growth of two dryland wheat cultivars

Change in plant physiological relationships especially in photosynthesis under drought stress can affect light absorption and the final yield of the crop. Improving the parameters related to photosynthesis in order to increase or decrease the loss of assimilation under drought stress is one of the ways of crop management. The effect of three growth hormones (3 indoleacetic acid [IAA], gibberellic acid [GA3] and 6 benzylaminopurine [6 BAP]) via control (distilled water) was evaluated at booting stage of two wheat cultivars (Rijaw and Azar 2). A factorial experiment using a randomized complete block design (RCBD) with three replications was setup at the Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran during 2014-15 and 2015-16. The results showed that 6-BAP and IAA produced the highest grain yield in the Rijaw cultivar with averages of 1800 and 1700 kg.ha-1, respectively. Also, the highest mean of specific leaf weight (86 mg.cm-2), photosynthesis rate (18.6 μmol CO2.m-2.s-1) and photosynthetic water use efficiency (667 μmol CO2.mol-1H2O) were related to the application of 6-BAP on Rijaw cultivar. The photosynthetic rate had a positive and significant correlation with specific leaf weight (R2= 0.92), photosynthetic pigments content(R2= 0.98) and mesophilic conductivity (R2= 96). Also, the Rijaw cultivar was superior to Azar-2 in all traits. In general, it can be concluded that the external application of various growth hormones in the critical stages of growth and development of wheat improves the photosynthetic capacity of the plant. This will reduce the final grain yield loss under drought stress conditions.