Functions and Toxicity of Chromium on Plants Physiological and Molecular Aspects: A Review

Abstract

Chromium exists in a variety of different oxidation states and is a polyvalent element; only trivalent chromium (III) and hexavalent chromium (VI) are found frequently in the natural environment. The biogeochemical procedures that regulate Cr (VI) mobilization, accumulation, bioavailability, toxicity in soils are discussed. Plants growing in chromium (VI) contaminated soils show reduced growth and development with lower agricultural production and quality. Furthermore, chromium (VI) exposure causes oxidative stress due to the production of free radicals that modifies plant morpho-physiological and biochemical processes at tissue and cellular levels. Nevertheless, plants may develop extensive cellular and physiological defensive mechanisms in response to Cr (VI) toxicity to ensure their survival. Chromium toxicity of (VI), plants avoid absorbing from either, soil or turn on the detoxifying mechanism, which involves producing antioxidants through enzymatic and non-enzymatic mechanisms for scavenging of reactive oxygen species. Chromium adversely affects the morphological and biochemical attributes of plants such as transport of nutrients, enzymatic activities, photosynthesis and overall maturation and development. Resistant of chromium varieties and mutation of targeted genes and can be selected to check the phytotoxicity and reduce the productivity of economically significant crops. There are very less number of plant species capable of hyper accumulating chromium in their shoot tissues. Mechanisms of detoxification role of organic ligands such as phytochelatins, methionine, glutathione, proteins, vitamins and amino acids are should be fully studies.