Abiotic Stress Response in Plants: The Relevance of Tocopherols

Abstract

In the natural environment, plants are continuously exposed to a variety of abiotic stresses yielding higher concentrations of reactive oxygen species (ROS), which may cause strong oxidation of cellular structures. To cope with oxidative stress plants have evolved very efficient antioxidant machinery, among which, lipophilic tocopherols represent an important nonenzymatic component. Tocopherol exists in four isomeric forms (α-, β-, γ-, δ-) and its composition depends on plant genotypic features and tissue type. It plays a crucial role together with other antioxidants (e.g., ascorbic acid, carotenoids, glutathione) in detoxifying ROS that emerge during stress conditions. As a component of thylakoid membranes, tocopherol acts as an important scavenger of singlet oxygen and other ROS thereby preventing lipid peroxidation and maintaining stable redox status in plant cells. In addition, tocopherols may protect the embryo from ROS during germination, under both aging and stress conditions. In this chapter, the role of tocopherols in the regulation of abiotic stress responses in plants will be emphasized.