Heavy Metals Toxicity in Plants: Understanding Mechanisms and Developing Coping Strategies for Remediation: A Review

Abstract

Heavy metal (HM) contamination is an increasing environmental and agricultural concern due to the persistence, toxicity, and bioaccumulative nature of metals such as cadmium (Cd), lead (Pb), mercury (Hg), and arsenic (As). These pollutants are primarily introduced through industrial effluents, mining, and agrochemicals, negatively impacting soil health, crop productivity, and food safety, ultimately posing serious risks to both ecosystems and human health. Conventional remediation methods can be costly, labor-intensive, and environmentally disruptive. Heavy metals like Cd, Pb, Hg, and As disrupt cellular homeostasis, inhibit photosynthesis, generate oxidative stress, and interfere with nutrient uptake, leading to significant yield losses in plants. In response to these stresses, plants utilize complex molecular mechanisms for tolerance, including the activation of antioxidant enzymes, upregulation of metal transporters, production of metal-chelating molecules, and modulation of stress-responsive genes and transcription factors. In contrast, bioremediation offers a sustainable and eco-friendly alternative by leveraging the detoxification capabilities of plants, microbes, and their symbiotic interactions. Techniques such as phytoremediation, microbial-assisted remediation, and integrated strategies involving biochar and organic amendments have demonstrated promising results in restoring heavy metal-contaminated soils. Recent advancements in molecular biology and synthetic biology have further improved the efficiency of bioremediation through the genetic engineering of hyperaccumulator plant species and metal-resistant microbes. This review examines the toxic effects of heavy metals on plants and highlights innovative, nature-based remediation strategies, emphasizing their potential for scalable and sustainable environmental cleanup.