Cadmium toxicity in plants: from transport to tolerance mechanisms

Cadmium (Cd), a non-essential heavy metal, induces severe phytotoxicity through oxidative stress and cellular homeostasis disruption. Chronic Cd exposure inhibits plant growth via leaf chlorosis, stunted stem elongation, and impaired root architecture, while disrupting physiological functions through chlorophyll degradation, membrane peroxidation, and antioxidant system collapse. This review systematically investigates plant adaptive responses to Cd stress. It examines the processes of Cd uptake pathways, translocation dynamics, physiological toxicity, and molecular defense mechanisms. Key findings highlight two main protective strategies: avoidance mechanisms involving root secretion regulation, cellular compartmentalization, efflux transport, and the other through chelation, antioxidant systems, and phytohormonal regulation in tolerance mechanisms. A particular emphasis is placed on the coordinated actions between metal-chelating compounds (including PCs, MTs, and MTPs) and both enzymatic (SOD, CAT) and non-enzymatic antioxidants. These insights advance the theoretical framework for plant Cd resistance and inform innovative implications for developing effective remediation approaches.