Plant-Chromium Interactions: From Toxicity to Remediation

Abstract

Chromium has a very widespread application in various industrial processes. Hence, it accounts for a large amount of release from industrial effluents, which leads to its accumulation in the environment beyond the recommended values. Soil serves as one of the major sinks for various anthropogenic sources, which further leads to its effects on plants. Chromium interactions in plants vary depending on oxidation state of Cr, pH, its speciation, concentration, type of plants and part of the plants. Both roots and shoots can accumulate Cr, but a major portion (98%) of absorbed Cr is accumulated in roots followed by stems and leaves. At lower concentrations Cr is found to enhance plant growth in certain species; however, higher concentrations are always detrimental, affecting seed germination, root and shoot growth, leaf number and morphology and the grain yield. Changes in metabolic pathways lead to alterations in genes, enzymes, proteins and antioxidants which help plants to tolerate and survive under Cr stress. The mechanisms are used by plants to phytoremediate chromium in soils. Several hyperaccumulators have been identified with high potential in accumulation of chromium. This can hence serve as an emerging cost-effective technology in remediating chromium-polluted sites.