Abstract/Summary

In a continuously changing environment plants are exposed to adverse stress conditions, such as sunlight, drying, cold, salinity, pollution, or heavy metals, which influence plant growth and result in the generation of reactive oxygen species (ROS). These small and highly reactive molecules have important cell signalling information concerning the change in the environmental and developmental conditions when maintained at proper cellular concentrations. However, during stress conditions, ROS levels in cells can greatly increase and cause oxidative stress by modifying other reactive species, proteins, or lipids. Therefore, appropriate regulation of ROS has a significant impact on plant development, growth, and survival. Ascorbic acid (AsA) as a major antioxidant in plant cells and its oxidized form dehydroascorbate (DHA) play a key role in redox state-based signalling mechanisms by detoxification of ROS and its products, as well as transmission of redox signals. Furthermore, DHA by itself also presents unique functions: cell cycle progression sensing and regulation, modulation of metal stress responses, and DHA adducts seem to be involved in oxidative stress-mediated cellular toxicity. It has become clear that the changes in the pool and ratio of the AsA/DHA redox pair by both growth and environmental cues modulate gene expression and protein levels resulting in increased stress tolerance. In the recent years, this important redox couple (AsA/DHA) has been of increasing interest to better understand the mechanisms of adaptive plant responses and stress tolerance towards abiotic and biotic stress. In this chapter, an overview of the literature is briefly presented in terms of the role of AsA/DHA redox pair in plant growth, and abiotic and biotic stress tolerance.