Antioxidant Defense Mechanism in Plants Exposed to Mercury Toxicity: Response, Tolerance and Remediation

In the current era of industrialization, the presence of mercury in the soil as a result of anthropogenic and natural processes is a topic of concern on a worldwide scale since it adversely impacts agricultural productivity, the environment, and human health. The toxicity of mercury results in oxidative damage, which seriously impairs plant growth and productivity. The defense mechanisms of plants against mercuric toxicity have recently been the subject of in-depth investigation. Plants exposed to mercury resulted in reduced root growth, shoot growth, plant height, relative water content, biomass production, chlorophyll content, photosynthetic rate, stomatal conductance, carbon assimilation with enhanced hydrogen peroxide production, free radicals or superoxides, malondialdehyde production. In order to cope with the oxidative stress caused by mercury, plants have evolved a number of adaptive strategies, including the accumulation of enzymatic and non-enzymatic antioxidants (Catalase, Peroxidase, Ascorbic acid, Super oxide dismutase, Phytochelatin, Metallothioneins), osmolytes like proline, and polyamines (PAs), which control a plant's normal growth and development while surviving in metal-contaminated urban and sub-urban areas. These biomolecules facilitates in inducing tolerance and resistance towards mercury by the plants.