Exogenous regulation of plant physiology is a kind of effective approach to help plant grow under Cd (cadmium)-contaminated environment. CA (cinnamaldehyde) is an environmental friendly natural compound with medicinal properties and antimicrobial activities. In this work, we found that CA was able to confer plant Cd tolerance by priming defense in the root of B. rapa. Pretreatment with CA attenuated the phytotoxicity induced by subsequent Cd stress, such as root growth inhibition, ROS accumulation, oxidative injury, and cell death in root tip. Cd stress decreased the intracellular Ca²⁺ level in roots, which could be enhanced by pretreatment with CA. Pretreatment with a Ca²⁺ chelator or a Ca²⁺ channel blocker blocked all the beneficial effects of CA on the increase in the intracellular Ca²⁺ level and the amelioration of physiological injury in roots under Cd stress. Correlation analysis combined with cluster analysis suggested that CA was able to prime plant defense by regulating endogenous Ca²⁺ in order to facilitate Cd tolerance. These results shed a new light on the novel role of CA in modulating plant resistant physiology against metal stress, which may extend our knowledge on both CA and plant Cd tolerance.

植物生理的外源调节是一种帮助植物在镉（Cd）污染环境下生长的有效方法。CA（肉桂醛）是一种具有医学特性和抗菌活性的环保天然化合物。在这项工作中，我们发现CA可以通过在B. rapa的根中引发防御来赋予植物对Cd的耐受性。用CA预处理可减轻随后的Cd胁迫引起的植物毒性，例如根生长抑制，ROS积累，氧化损伤和根尖细胞死亡。Cd胁迫降低了根部细胞内Ca ^2+的水平，这可以通过用CA预处理来增强。用Ca ²⁺螯合剂或Ca ^2+进行预处理通道阻滞剂阻​​断了CA对Cd胁迫下根部细胞内Ca ²⁺水平增加和根系生理损伤改善的所有有益作用。相关分析与聚类分析相结合表明，CA能够通过调节内源Ca ²⁺来增强植物对Cd的耐受性，从而启动植物防御。这些结果为CA在调节植物对金属胁迫的抗性生理中的新作用提供了新的启示，这可能会扩展我们对CA和植物对Cd的耐受性的知识。