Spectrophotometric Assays to Evaluate the Rhizospheric Microbes Mediated Drought Tolerance in Plants

Abstract

Drought stress is the most threatening environmental effect which limits the growth and productivity of plants globally. It is considered to cause oxidative stress in plants which results in the accumulation of reactive oxygen species. Oxidative stress is defined as an imbalance between antioxidants and reactive oxygen species (ROS) in response to any environmental stress. The antioxidant defence machinery protects plants against oxidative stress damages. Plants possess very efficient enzymatic (superoxide dismutase, SOD; catalase, CAT; polyphenol oxidase; guaiacol peroxidase), non-enzymatic (ascorbic acid, ASH; glutathione, GSH; phenolic compounds), and osmolyte (proline and soluble sugars) antioxidant defence systems which work in concert to control the cascades of uncontrolled oxidation and protect plant cells from oxidative damage by scavenging of ROS. Various soil microorganisms such as arbuscular-mycorrhizal fungi or plant growth-promoting rhizobacteria (PGPR) are the obligate symbionts that can improve plant tolerance to drought stress by increasing both plant nutrition and antioxidant defence system against the oxidative stress produced by water scarcity. In a natural soil, rhizosphere competence needs to be considered for successful interactions between these microorganisms and plants to overcome the environmental stress problem. In this chapter, we centred the assay/protocols to evaluate this relationship of antioxidant machinery and rhizospheric microbes by various spectrophotometric biochemical assays.