Antioxidant Defense: A Key Mechanism of Cadmium Tolerance

Cadmium (Cd) is a persistent soil pollutant, with high toxicity to plants and humans. Its availability to plants is affected by several factors, including pH of the soil, while its accumulation in the plants is related to the plant’s tolerance, genotype, environmental factors, etc. As a response to oxidative stress induced by heavy metals plants activate antioxidant response, which consists out of enzymatic and nonenzymatic components. Enzymatic antioxidant system in plants includes enzymes such as superoxide dismutase, peroxidases, and catalases, while nonenzymatic antioxidant system includes molecules with ability to scavenge radicals. Antioxidant molecules mainly responsible for nonenzymatic antioxidant response in plants are ascorbate, tocopherol, carotenoids, and flavonoids. Effective antioxidant system is related to plants’ tolerance to Cd and numerous research have demonstrated that increased levels of antioxidant enzymes and molecules can alleviate Cd stress and increase Cd accumulation levels in plants.