Phenolic content changes in plants under salt stress

Abstract

Phenolics are one of the main group of plant secondary metabolites, including over 9,000 various compounds. They possess a wide range of biological functions in plants, such as protection from UV light, defense against pathogens, pigmentation to attract pollinators and protection from reactive oxygen species generated when aerobic or photosynthetic metabolism is impaired by various environmental stresses such as salt stress. Soil salinity is a major environmental constraint to plant growth and productivity and is an especially serious problem in agricultural systems that rely heavily on irrigation. Salt stress causes an over-reduction of photosynthetic electron chain and promotes the production of reactive oxygen species (ROS) and therefore oxidative stress. Higher plants have developed different adaptive mechanisms to reduce oxidative damage resulting from salt stress, through the biosynthesis of a cascade of antioxidants. Among them, phenolic compounds such as phenolic acids, flavonoids and proanthocyanidins play an important role in scavenging free radicals. The aim of this chapter is to discuss recent results on the phenolic compound changes in plants under salt stress. Phenolic content in plants, and their antioxidant activity, depend on biological factors (genotype, organ and ontogeny), as well as edaphic, and environmental conditions (temperature, salinity, water stress and light intensity). The reviewed results indicate the importance of plant tissue, species as well as salt doses, time of salinity exposure and initial levels of phenolics in determining phenolic response to salinity.