The Role of Ascorbate‐Glutathione Pathway in Reactive Oxygen Species Balance Under Abiotic Stresses

Plants undergo different abiotic stresses such as water limitation (drought, flooding), ion imbalance (salinity, inappropriate levels of metals [metalloids]), extreme light intensities and temperature regimes (heat, cold) as well as combinations of these negative influences, for instance drought, heat, and high insolation. Under these unfavorable conditions, reactive oxygen species (ROS) are produced in excess causing oxidative stress. Plants mobilize antioxidant system to protect cellular and sub-cellular compartments from this destructive impact using antioxidant enzymes as well as non-enzymatic compounds. Ascorbate-glutathione pathway is an important component of plant antioxidant defense to reduce excessive amount of hydrogen peroxide. Cellular buffers (glutathione and ascorbic acid) as well as four enzymes (ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase) are involved in this cycle. There are different subcellular isoforms of each of the antioxidant enzymes and each isoform differentially responds to different stresses. The mechanisms of each isoform regulation by abiotic stress(es), in particular under different developmental stages, are yet to be completely understood. The importance of ascorbate-glutathione pathway for crosstalk between ROS and reactive nitrogen species in abiotic stress tolerance has also been investigating. Considering recent data obtained from physiological, biochemical and molecular genetic studies, the current chapter discusses significance of the ascorbate-glutathione pathway in abiotic stress-exposed model and crop plants, also highlights unexplored aspects in the current context for future studies.