Evaluating Application of Salicylic acid and Seaweed Extracts on some Physiological Traits of White Bean (Phaseolus lanatus L.) under Drought Stress Conditions

Drought is one of the most important factors limiting the growth and yield of plants in many parts of the world. In order 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 in both Islamabad and Khorramabad regions. Main factor consisted of three levels of irrigation (equivalent of 60 mm: Normal, 90 mm and 120 mm of accumulated evapotranspiration from evaporation class A pan. Sub factor consisted of 8 different levels of salicylic acidapplication (0.5 molar), no application of salicylic acid, 4 levels of seaweed extracts (0, 50, 100 and 150 gram) per plot. Results of this study showed that drought stress decreased photosynthesis rate and chlorophyll content, but the salicylic acid increased both the photosynthesis rate and chlorophyll content. Drought stress also increased proline content, ion leakage from the membrane and antioxidant enzymes activities such as catalase, ascorbate peroxidase and superoxide dismutase, while it 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 120 mm evaporation pan (drought stress treatment) and no application of seaweed, and the highest grain yield was obtained from 60 mm evaporation pan (drought stress level) and 150 g seaweed treatments. Application of seaweed enhanced the grain yield production. Application of salicylic acid also increased grain yield up to 4.5%. According to the results of this study, it seems that salicylic acid and seaweed could reduce some negative effects of drought stress.