2.7. Altering antioxidant defense system
Exposure of plants to drought stress leads to the generation of
reactive oxygen species (ROS), including superoxide anion radicals
(O2
−), hydrogen peroxide (H2O2), hydroxyl radicals (OH), singlet
oxygen (O12) and alkoxy radicals (RO). ROS react with proteins,
lipids and deoxyribonucleic acid causing oxidative damage and
impairing the normal functions of plant cell. In order to over-come
these effects, plants develop antioxidant defense systems comprising
both enzymatic and non-enzymatic components that serve
to prevent ROS accumulation and alleviate the oxidative damage
occurring during drought stress (Miller et al., 2010). Enzymatic
components include superoxide dismutase (SOD), catalase (CAT),
ascorbate peroxidase (APX), and glutathione reductase (GR). Nonenzymatic
components contain cysteine, glutathione and ascorbic
acid (Kaushal and Wani, 2015).