Effects of transpiration reducers on white beans under drought stress conditions

The effects of seaweed fertilizer and salicylic acid (SA) as a transpiration reducer on the yield and physiological traits of white beans (the Almas variety) were investigated in a split-split plot experimental design with three replications in two locations, West Islamabad and Solaymanieh, in the crop year 2017-2018. The main plots were the application of three stress levels (60, 90, and 120 mm of surface evaporation from a Class A evaporation pan). In the subplots, treatments were foliar application of seaweed fertilizer at 0, 50, 100, and 150 g/ha, and two levels of foliar application and no SA foliar application were applied in the sub-subplots. The results showed that the two selected experimental locations were significantly different in climatic characteristics (average temperature and rainfall). The highest grain yield was obtained from the Islamabad region. Drought stress caused a decrease in grain yield and its related traits, as well as an increase in oxidative damage and ion leakage from membranes. Drought stress activated the antioxidant defense system and reduced water use efficiency. Moreover, drought stress reduced both the photosynthetic rate and chlorophyll content, and seaweed and SA spraying increased these two traits. Proline content, ion leakage, and the activity of antioxidant enzymes (catalase, ascorbate peroxidase, and superoxide dismutase) increased due to drought stress. SA application increased the activity of antioxidant enzymes, but the response to SA was not similar in different seaweed concentrations. Drought stress also increased proline content and the ion leakage rate from the membrane and decreased grain yield.