Non-Enzymatic Antioxidants in Stressed Plants: A Review

Plants are exposed to different ecological stress during their life cycle, and because of these tensions, free radicals are shaped. Reactive oxygen species(ROS) have a fundamental ability to support typical plant improvement and stress tolerance. The disruption of the proportionality of ROS generation and antioxidant defense systems is one of the primary effects of biotic and abiotic stress, resulting in an excess of ROS buildup and oxidative damage in plants. Plants may combat this issue by producing ROS-neutralizing compounds, and both enzymatic and non-enzymatic antioxidant defense mechanisms maintain the proper ratio between ROS generation and detoxification. Ascorbic acid (AsA), glutathione (GSH), flavonoids, Vitamin E (α-tocopherols), and carotenoids are crucial non-enzymatic antioxidants in this context, with a high potential for performing a variety of crucial activities in plants under both stressful and unstressful conditions, in addition to scavenging ROS. This review illustrates the main roles of some non-enzymatic antioxidants in plants subjected to various types of biotic and abiotic stresses.