Seaweed extract effect on water deficit and antioxidative mechanisms in bean plants (Phaseolus vulgaris L.)

The effect of seaweed extract (SWE) obtained from two macroalgae species, Ulva rigida and Fucus spiralis, on drought stress tolerance in green bean plants (Phaseolus vulgaris L.) was studied. Examination of growth parameters and some physiological and biochemical parameters showed that SWE extract enhanced vegetative growth in bean plant without stress and in plant under drought stress condition. Maximal plant height and dry weight were observed with application of 25 % U. rigida and F. spiralis extract. Enhanced chlorophyll a (Chl a) and chlorophyll b (Chl b) pigments and glycine betaine (GB) content were also observed with all SWE treatments under water deficit. The lipid peroxidation was low pronounced in stressed plants treated with SWE. Total phenolic content was increased in bean plants under different growth conditions (without stress (WS), moderate water stress (MWD), and severe water deficit (SWD)) and treated with SWE at all concentrations. The highest total phenolic content was attained with the application 25 % U. rigida extract in bean plant subjected to drought stress (MWD and SWD). There was a significant enhancement of superoxide dismutase (SOD) activity and catalase (CAT) activity with SWE treatment in plant under moderate water deficit. Plants stressed and treated with SWE showed maximal ascorbate peroxidase (APX) activity. The increased total phenolic content and the enhancement of antioxidant enzymatic activity by SWE in stressed bean plants may contribute to protection against peroxidation and reduce the severity of water deficit.