The effect of foliar application of Atrazine on stomatal and nonstomatal control factors of photosynthesis in safflower in drought stress condition

Drought stress is one of the most important and most common environmental stresses that limit plant growth in the face. In this path، photosynthesis is main determinant for plant growth and retention ability at environmental stresses is important for preservation of growth stability. for study of the role of stomatal and nonstomatal factors on photosynthesis in safflower (Carthamus tinctorius cv. Sina) in Miyaneh region. A factorial experiment with randomized complete block design (RCDB) and three replications were applied. That at it foliar application of atrazine as a antitranspirant were at 3 phenological stage (steming، flowering and seed filling stages). The antitranspirant application rates were 0 (control)، 80، 120 and 160 gr. ha-1. By the results of analysis of varians (ANOVA) showed that between rates foliar application at all times on physiologic charactristics as photosynthesis rate، transpiration severity، intercellular (Ci)، stomata conductivity، mesophyll conductivity and relative water content (RWC) was significant. This in study foliar application of Atrazine to content 120 gr. ha-1 in flowering time had highest effect on this characters except RWC. The highest RWC were obtained at 120 (gr. ha-1) in steming time. Between rates foliar application of Atrazine than photosynthesis water use efficiency (PWUE) were significant as highest PWUE were obtained at 120 gr. ha-1. Evaluation of characteristic''s correlation showed that there were a positive and significant correlation was found between photosynthesis with characteristics such as transpirant rate، mesophyll conductivity، Ci and stomata conductivity.