Effect of foliar application of seaweed Ascophyllum nodosum extract on morpho-physiological characteristics of bean (Phaseolus vulgaris) under water stress

Seaweed extract can improve the physicochemical properties of the soil and has a favorable effect on the plant growth and development due to having high nutrient content, high water holding capacity, plant growth regulators and beneficial microorganisms. The aim of this experiment was to investigate the effect of Ascophyllum nodosum extract, a brown alga, on the morphophysiological characteristics of bean plant (Phaseolus vulgaris) under water stress. The experiment was performed in a Completely Randomized Factorial Design with three replications. Experimental treatments included 4 concentrations of foliar application of seaweed extract (0, 0.2, 0.4 and 0.6%) and 3 levels of water stress including no stress, mild stress and severe stress (irrigation at 75, 50 and 25% of field capacity, respectively). The results showed that the interaction effects of stress and algal extract on the evaluated traits were not significant. However, the seaweed extract significantly increased the leaf area, number of the leaves, leaf length, surface and length of the roots, root dry weight, the content of chlorophyll a and b and the total chlorophyll content. Application of algal extract at levels of 0.2 and 0.4% caused a significant increase in the evaluated parameters as compared with the control plants. The evaluation of water scarcity stress effects showed a significant reduction in the all studied characteristics in accordance with increasing water stress level from 75% to 25% of field capacity. The results of this study showed that foliar application of seaweed extract significantly increased some morphological and photosynthetic properties, while water stress significantly reduced the investigated parameters.