Exogenous Ascorbic Acid Mediated Abiotic Stress Tolerance in Plants

Ascorbic acid (AsA) plays various roles in regulating plant responses or tolerance to environmental stresses. The positive effects of exogenous AsA application are well documented, ranging from seed germination to biomass or yield production, particularly under various abiotic stress conditions. AsA is well known for its roles in ameliorating oxidative damages on plant growth, physiological and metabolic processes by activating nonenzymatic and enzymatic components of antioxidant metabolism. Exogenous AsA application also mitigates stress-inhibition of photosynthesis, delays leaf senescence or loss of chlorophyll, and helps maintain cell membrane stability. In addition, AsA also facilitates the maintenance of ion homeostasis (i.e., Na+, K+, Mg2+, Ca2+) in plants exposed to abiotic stress. Interactions between AsA, phytohormones, and other metabolites also play roles in regulating plant growth and stress adaptation. This chapter provides an overview of physiological, biochemical, and molecular effects of exogenous application of AsA for various plant species under abiotic stresses. Future research addressing transcriptomic, proteomic, and metabolomic profiles will provide further insights into mechanisms of improved growth and stress tolerance brought by exogenous application of AsA.