Exogenous superoxide dismutase mitigates cell damage in drought-sensitive peanuts
The superoxide dismutase (SOD) enzyme initiates the process of neutralization of cytotoxic effects caused by reactive oxygen- species (ROS). In drought-tolerant plants, SOD is rapidly supplied due to their ability to adjust when they sense a lack of water, unlike in drought-sensitive plants. To investigate whether exogenous application of SOD could benefit drought-sensitive plants by ameliorating water stress, we tested two contrasting cultivars, BR 1 and IAC Caiapó, which are drought tolerant and sensitive cultivars, respectively. Plants of both cultivars were grown in pots in a greenhouse and submitted to nine days of water suppression starting at V1 phase, and treated with SOD at different concentrations, 11, 23 and 34 µg mL-1, applied to both adaxial and abaxial surfaces of leaves. The status of water stress was estimated through verification of soil moisture in stressed treatments, in comparison with controls. Additionally, stomatal conductance was estimated to evaluate stomata closing. The plants were assessed for growth, gas exchange, and activity of antioxidative enzymes. Overall, the contribution of exogenous SOD in mitigating the effects of water stress was greater in stressed plants of drought-sensitive cultivars. Gas exchange recovery was observed in the plants even with the lowest applied SOD concentration (11 µg mL-1), whereas higher exogenous SOD supply was required to prevent oxidative damage. More in-depth studies regarding the potential benefits of this type of treatment on the phenology of runner genotypes are merited, since these cultivars are very productive, though highly sensitive to water restriction.