Study on the physiological and metabolic mechanisms of exogenous quercetin in cadmium hyperaccumulator Amaranthus hypochondriacus L

Introduction: Improving cadmium (Cd) tolerance and phytoremediation efficiency in hyperaccumulator plants is a critical scientific issue in environmental remediation. Remediation performance is often constrained by physiological bottlenecks, including insufficient tolerance to high Cd stress and low heavy metal accumulation capacity. Against this background, exploring effective strategies to enhance the phytoremediation efficiency of hyperaccumulators has important theoretical and practical value. Methods: ; denoted as CK, Q1, Q2, and Q3, respectively) was applied under varying Cd levels (0, 4, 20 mg·kg⁻¹; denoted as Cd0, Cd4, and Cd20, respectively), and physiological traits, antioxidant responses, and key metabolites were comprehensively assessed. Results: The results demonstrate that exogenous quercetin markedly alleviated Cd induced toxicity, with the Cd20Q2 treatment showing the most pronounced mitigation effect. Compared the Cd stressed control without quercetin, electrolyte leakage was reduced by 49.5%, chlorophyll content increased by 17.7%, and the plant's Cd enrichment capacity was significantly enhanced, with the aboveground enrichment factor reaching 7.02. It revealed that quercetin activated the phenylpropanoid flavonoid pathway, promoting the synthesis of endogenous flavonoids (notably quercetin and kaempferol) and increasing glutathione (GSH) levels and overall antioxidant capacity. This created a synergistic mechanism of "endogenous flavonoid enhancement coupled with exogenous quercetin supplementation". Concurrently, the enhanced accumulation of GSH and related metabolites facilitated Cd chelation and detoxification, thereby reducing oxidative injury at the cellular level. Discussion: In summary, exogenous quercetin improves Cd tolerance and remediation efficiency in amaranth by regulating flavonoid metabolism and strengthening GSH mediated detoxification. These findings provide theoretical and practical support in heavy metal remediation strategies.