Effects of Salicylic Acid and Seaweed (Ascophyllum nodosum) Extracts Application on some Physiological Traits of White Bean (Phaseolus lanatus L.) under Drought Stress Conditions

Drought is one of the most important growth and yield limiting factors of crop plants in many parts of the world. To investigate the effects of drought stress and seaweed extract and salicylic acid on some photosynthetic and photochemical traits of white bean plant, a split-factorial experiment, based on randomized complete block design with three replications was conducted in 2016-2017 growing season. The experiment was performed at two different locations: Islamabad and Khorramabad. Main factor consisted of three levels of irrigation (irrigation after 60 mm, 90 mm and 120 mm of accumulated evapotranspiration of class A pan evaporation and sub-plots of 8 different levels of salicylic acidapplication (0.5 molar), no application of salicylic acid, 4 levels of seaweed extracts applications 0, 50, 100 and 150 grams. Results of this study showed that drought stress decreased the rate of photosynthesis and chlorophyll content, but the salicylic acid increased both the rate of photosynthesis and chlorophyll content. Drought stress also increased proline content, ion leakage from the membrane and antioxidant enzyme activities such as catalase, ascorbate peroxidase and superoxide dismutase and reduced the grain yield. Application of salicylic acid increased the activity of antioxidant enzymes, but the response to salicylic acid was not similar in various levels of seaweed. The lowest grain yield was obtained from  irrigation after 120 mm evaporation and without application of seaweed. Highest grain yield was obtained from irrigation after 60 mm evaporation and 150 g. seaweed treatment. Application of seaweed enhanced the grain yield production. Application of salicylic acid also, increased grain yield by 4.5%. According to the results of this study, it seems that application of salicylic acid and seaweed may reduce some negative effects of drought stress.