Molecular and Cellular Mechanisms of Plant Responses to Heavy Metal Stress in Mining-Impacted Environments

Heavy metal contamination associated with mining activities is a major source of abiotic stress for plants, strongly affecting plant physiology, growth and survival in contaminated environments. Due to their non-biodegradable nature and long-term bioavailability, heavy metals persist in soils affected by mining activities, exposing plants to chronic stress conditions that require the activation of coordinated cellular and molecular response mechanisms to limit toxicity and maintain internal homeostasis. This review synthesises and critically analyses current knowledge on the molecular and cellular mechanisms governing plant responses to heavy metal stress in mining-affected environments. Key processes involved in metal uptake and transport, redox imbalance and oxidative stress generation, antioxidant defence systems, and molecular detoxification mechanisms, including metal chelation, subcellular compartmentalisation, and gene expression regulation, are discussed. Particular attention is paid to cellular signalling pathways that mediate plant adaptation to prolonged exposure to complex metal mixtures. Emphasis is placed on integrating molecular-level knowledge with the specific context of mining sites, highlighting the limitations of extrapolating results obtained under controlled experimental conditions to naturally contaminated environments. This perspective integrates molecular mechanisms with the geochemical realities of mining sites, providing a solid basis for the development of effective phytoremediation strategies and the optimisation of plant species selection.