Physiological, biochemical, and molecular responses of the plants against enhanced ultraviolet B and heavy metal stress

Abstract

Ultraviolet-B (UV-B) radiation and heavy metals (HMs) are well-known stress factors for plants. UV-B is a part of incoming solar radiation reaching to the earth surface and its intensity is regulated by the stratospheric ozone layer, which in recent time had shown a significant depletion due to several natural and anthropogenic factors. HMs have also increased in the environment due to the industrial discharge, emissions from vehicle exhaust and improper disposal of wastes in soil and water, which directly or indirectly influence all types of vegetation. It is impor-tant to identify physiological, biochemical, and molecular changes in plants against stress factors and plant’s strategy to survive successfully under such harsh environment. This review primarily focuses on how UV-B and HMs individually or in combination elicit plant responses, their survival and various adaptation mechanisms in combating stress. Both stresses affect various physiological and biochemical processes at cellular and molecular levels in plants. Induction of several important metabolites such as N-containing compounds, phenolic compounds, terpenes, and essential oils is the major secondary response in plants for long-term stress adaptation under UV-B stress whereas sequestration of HMs by the formation of metal-ligand complex and the antioxidant defense systems are the most important detoxification mechanism used by plants against HMs-induced stress. Based on the outcomes, it will be possible to identify important traits, plants, and various defensive or adaptive mechanisms in plants to cope up with UV-B and metal tolerance.