Physiological responses of peanut (Arachis hypogaea L.) cultivars to water deficit stress: status of oxidative stress and antioxidant enzyme activities

From a field experiment, the changes in oxidative stress and antioxidant enzyme activities were studied in six Spanish peanut cultivars subjected to 25-30 days of water deficit stress at two different stages: pegging and pod development stages. Imposition of water deficit stress significantly reduced relative water content, membrane stability and total carotenoid content in all the cultivars, whereas total chlorophyll content increased at pegging stage but decreased at pod developmental stage. Chlorophyll a/b ratio increased under water defi cit stress in most of the cultivars suggesting a greater damage to chlorophyll b rather than an increase in chlorophyll a content. Oxidative stress measured in terms of H2O2, superoxide radical content and lipid peroxidation increased under water defi cit stress, especially in susceptible cultivars such as DRG 1, AK 159 and ICGV 86031. Relationship among different physiological parameters showed that the level of oxidative stress, in terms of production of reactive oxygen species, was negatively correlated with activities of different antioxidant enzymes such as superoxide dismutase, catalase, peroxidase, ascorbate peroxidase and glutathione reductase. In conclusion, the study shows that water defi cit stress at pod development stage proved to be more detrimental than at pegging stage. The higher activities of antioxidant enzymes in the tolerant cultivars like ICGS 44 and TAG 24 were responsible for protection of oxidative damage and thus provide better tolerance to water defi cit stress.