Bioremediation of Cadmium through Hyperaccumulating Plants: Mechanisms, Molecular Pathways and Future Prospects

Abstract

Cadmium (Cd) is a toxic heavy metal that significantly endangers both environmental and human health. Its presence in soil and water can have devastating effects on ecosystems, and it can accumulate in the food chain, leading to serious health problems for humans. Fortunately, nature offers a powerful and elegant solution to this problem: phytoremediation. Phytoremediation is an eco-friendly and cost-efficient strategy that employs plants to extract, neutralize, or immobilize environmental contaminants. Unlike conventional remediation techniques, it offers a sustainable solution for pollutant removal. Certain plant species are capable of absorbing cadmium from the soil through their root systems. Some of these plant species, termed ‘hyperaccumulators,’ exhibit an exceptional capacity to sequester elevated levels of cadmium within their biomass, predominantly localizing the metal in foliar and stem tissues These plants act as green sponges, effectively extracting the metal from the soil. Once absorbed, cadmium is transported throughout the plant via the vascular system. In some cases, plants can efficiently translocate cadmium from their roots to their shoots, making it easier to remove the metal from the contaminated site by harvesting the plant biomass. Plants can also stabilise cadmium in the soil by reducing its bioavailability. This can be achieved through various mechanisms, such as the release of organic acids that bind to cadmium, preventing it from leaching into groundwater or being taken up by other organisms.