Melatonin (M) is a pleiotropic molecule that improves plant growth and increases heavy metal tolerance. The role of M for improving plant growth and tolerance under cadmium (Cd) stress, and mitigation of Cd-induced toxicity has not yet been sufficiently examined. Therefore, here we conducted a glasshouse experiment to explore the influence of various M dosages on Cd detoxification and stress-tolerance responses of Brassica napus under high Cd content (30 mg kg⁻¹). The effects of M on the modulation of Cd tolerance in B. napus plants have been investigated using various growth attributes, Cd accumulation and tolerance indices, and secondary metabolic parameters. We found that Cd stress inhibited root growth (by 11.9%) as well as triggered reactive oxygen species accumulation (by 31.2%) and MDA levels (by 18.7%); however, exogenous M substantially alleviated the adverse effect of oxidative stress by decreasing levels of H₂O₂ (by 38.7%), MDA (by 13.8%) and EL (by 1.8%) in the Cd-stressed plants, as compared to the M-untreated plants (control). Interestingly, exogenous M reduced Cd accumulation in roots (∼48.2–58.3-fold), stem (∼2.9–5.0-fold) and leaves (∼4.7–6.6-fold) compared to control plants, which might be due to an M-induced defense and/or detoxification response involving a battery of antioxidants. Overall, addition of the exogenous M to the Cd-stressed plants profoundly enhanced Cd tolerance in B. napus relative to control plants. These results suggested the biostimulatory role (at the physiological and molecular level) of M in improving growth, Cd tolerance, and Cd detoxification in B. napus, which indicate the potentiality of M for green remediation of Cd contaminated soils. This green trial would provide a reference for producing renewable bioenergy crops under Cd stress in contaminated soils. However, these recommendations should be verified under field conditions and the potential mechanisms for the interaction between Cd and M should be explicitly explored.

褪黑激素 (M) 是一种多效性分子，可促进植物生长并增加对重金属的耐受性。M 在镉 (Cd) 胁迫下改善植物生长和耐受性以及减轻镉诱导的毒性方面的作用尚未得到充分检验。因此，我们在这里进行了温室实验，以探索不同M剂量对高Cd含量（30 mg kg ^-1）下甘蓝型油菜Cd解毒和抗逆反应的影响。M 对欧洲油菜Cd 耐受性调节的影响已经使用各种生长属性、Cd 积累和耐受指数以及次生代谢参数对植物进行了研究。我们发现镉胁迫抑制根系生长（11.9%）并引发活性氧积累（31.2%）和MDA水平（18.7%）；然而，外源 M 通过降低 H ₂ O _{2水平显着减轻了氧化应激的不利影响}与未经 M 处理的植物（对照）相比，Cd 胁迫植物中的（38.7%）、MDA（13.8%）和 EL（1.8%）。有趣的是，与对照植物相比，外源 M 减少了根（~48.2-58.3 倍）、茎（~2.9-5.0 倍）和叶（~4.7-6.6 倍）中的镉积累，这可能是由于 M-诱导的防御和/或解毒反应涉及一系列抗氧化剂。总体而言，相对于对照植物，向受镉胁迫的植物中添加外源 M 显着增强了欧洲油菜对镉的耐受性。这些结果表明 M 在改善欧洲油菜的生长、镉耐受性和镉解毒方面的生物刺激作用（在生理和分子水平上），这表明 M 对 Cd 污染土壤的绿色修复的潜力。该绿色试验将为在受镉胁迫下在受污染土壤中生产可再生生物能源作物提供参考。然而，这些建议应在现场条件下进行验证，并应明确探索 Cd 和 M 之间相互作用的潜在机制。