pThis edited book highlights the molecular basis of various enzymatic and non-enzymatic antioxidants, defense mechanisms and adaptation strategies employed by plants to avoid the stressful conditions. Special focus is given to gene expression, omics and other latest technologies such as CRISPR-Cas mediated genome editing applications for defense related studies in plants. Environmental stresses such as drought, salinity or floods etc. induce the generation of reactive oxygen species ROS which causes severe damage to cell membrane integrity by accelerating lipid peroxidation. To counteract the detrimental effect of ROS, plants are inherited with an intricate and vibrant antioxidant defense system, comprised of enzymatic catalase, peroxidase, superoxide dismutase, glutathione reductase, glutathione S-transferase, guaiacol peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase etc., and non-enzymatic glutathione, ascorbate, 945-tocopherol, carotenoids, flavonoids etc. anti