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Variation in antioxidant metabolism of faba bean (Vicia faba) under drought stress induced by polyethylene glycol reveals biochemical markers associated with antioxidant defense

Abstract Antioxidative responses in faba bean plants subjected to different osmotic potentials induced by PEG-6000 were investigated. Drought stress significantly decreased photosynthetic gas exchange parameters (net CO2 assimilation rate, transpiration rate, internal concentration of CO2 and stomatal conductance) and leaf RWC in Bachar and Giza 3, while the magnitude of reduction in Bachar was relatively low. This could be due to its better antioxidant enzyme activities (catalase, superoxide dismutase and ascorbate peroxidase) and higher transcription levels of their respective genes. Moreover, the accumulation of proline and soluble sugars, combined with enhanced total phenolics content, total flavonoid content, and total antioxidant capacity may play important roles in drought tolerance in faba bean, thereby increasing osmotic adjustment and protection from free radicals. In agreement with this assumption, Bachar displayed lower MDA and H2O2 content and lower electrolyte leakage than Giza 3. Moreover, the detected increase in antioxidant enzyme activities appeared to be correlated with mRNA levels. Enzymatic and non-enzymatic (phenolic and non-phenolic) antioxidants may be useful as biochemical markers of oxidative stress responses to differentiate drought tolerant faba bean cultivars under drought stress. In the study, Bachar was found to be relatively tolerant to drought stress and Giza 3 was sensitive.