Abstract
Extensive industrial activities resulted in an increase in chromium (Cr) contamination in the environment. The toxicity of Cr severely affects plant growth and development. Cr is also recognized as a human carcinogen that enters the human body via inhalation or by consuming Cr-contaminated food products. Taking consideration of Cr enrichment in the environment and its toxic effects, US Environmental Protection Agency and Agency for Toxic Substances and Disease Registry listed Cr as a priority pollutant. In nature, Cr exists in various valence states, including Cr(III) and Cr(VI). Cr(VI) is the most toxic and persistent form in soil. Plants uptake Cr through various transporters such as phosphate and sulfate transporters. Cr exerts its effect by generating reactive oxygen species (ROS) and hampering various metabolic and physiological pathways. Studies on genetic and transcriptional regulation of plants have shown the various detoxification genes get up-regulated and confer tolerance in plants under Cr stress. In recent years, the ability of the plant to withstand Cr toxicity by accumulating Cr inside the plant has been recognized as one of the promising bioremediation methods for the Cr contaminated region. This review summarized the Cr occurrence and toxicity in plants, role of detoxification genes in Cr stress response, and various plants utilized for phytoremediation in Cr-contaminated regions.
Highlights
Heavy metal contamination is becoming a serious environmental issue worldwide for the past few decades due to their increased concentration beyond the permissible limit.Chromium (Cr) is a naturally occurring heavy metal and the 17th most abundant element in the earth’s mantle [1]
Brassica oleracea showed a decrease in leaf size, wilting, and chlorosis when grown in refined sand with complete nutritional media under 0.5 mM
Cr(VI) treated O. sativa seedlings showed that Cr stress induces the transcript levels of different antioxidant enzymes ascorbate peroxidase (APX), superoxide dismutase (SOD), peroxidase (POD), and glutathione peroxidase (GPX) coding genes in treated plants in comparison to control plants [75]
Summary
Heavy metal contamination is becoming a serious environmental issue worldwide for the past few decades due to their increased concentration beyond the permissible limit. Sustainability 2021, 13, 4629 mobility in the water system [1] Both valence states of Cr i.e., Cr(III) and Cr(VI) are taken up by plants [7]. Phytoremediation is a rapidly growing field of research for heavy metal contaminated regions. Numerous research studies have shown that many plant species are capable of effectively removing Cr from contaminated regions which could be useful for the phytoremediation process [13]. Cr hyperaccumulators, with their associated microflora, have been used around the industrial effluent sites to remove the excess toxic Cr, as well as organic matters. The review summarizes the recent development of sustainable approaches for Cr detoxification in the environment
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