Cadmium (Cd) pollution in soil severely affects crop production and food safety. Currently, cupric oxide nanoparticles (CuO NPs) are considered as potential regulators alleviating the toxicity of heavy metals in plants, but their physiological functions and molecular mechanisms are not completely clarified. In this study, we found that CuO NPs had the capacity to adsorb ionic Cd²⁺ and their suspension (≤100 mg L⁻¹) remained stable within 24 h. High concentrations of CuO NPs (≥10 mg L⁻¹) inhibited plant growth, while 5 mg L⁻¹ CuO NPs could be appropriate for Cd remediation in rice and barley. We also investigated the influence of 5 mg L⁻¹ CuO NP pre-treatment on growth and Cd toxicity of two rice genotypes (Nipponbare and 9311) and two barley genotypes (Golden Promise and XZ26) exposed to Cd stress. The results showed that pre-treatment with low concentration of CuO NPs (5 mg L⁻¹) alleviated Cd toxicity, which is attributed to inhibition of Cd uptake in roots related to CuO NPs adhering on the rhizosphere surface to inhibit Cd²⁺ influx, down-regulation of some key Cd-transporter genes (Nramp5 and HMA2), and enhancement of antioxidative capacity (SOD, POD and CAT) and up-regulation of ROS scavenging related genes. Moreover, the regulation of Cd-transporter and ROS scavenging related genes by CuO NP pre-treatment showed a little difference between paddy rice and upland barley, which may account for the difference in the response to Cd stress and CuO NP pre-treatment between them. It may be concluded that low concentration of CuO NPs alleviates Cd toxicity in plants acting as a nano-scale protector, and provides an alternative approach for fighting against Cd pollution.

中文翻译：

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氧化铜纳米颗粒减轻谷类作物中的镉毒性

土壤中的镉（Cd）污染严重影响农作物生产和食品安全。目前，氧化铜纳米粒子（CuO NPs）被认为是减轻植物重金属毒性的潜在调节剂，但其生理功能和分子机制尚未完全阐明。在这项研究中，我们发现CuO NPs具有吸附离子Cd ²⁺的能力，并且它们的悬浮液（≤100 mg L ^-1）在24小时内保持稳定。高浓度的 CuO NPs (≥10 mg L ^-1 ) 抑制植物生长，而 5 mg L ^-1 CuO NPs 可能适用于水稻和大麦中的 Cd 修复。我们还研究了 5 mg L ^-1的影响CuO NP预处理对两种水稻基因型（日本晴和9311）和两种大麦基因型（Golden Promise和XZ26）暴露于镉胁迫下的生长和镉毒性。^{结果表明，低浓度CuO NPs（5 mg L -1} ）预处理减轻了Cd毒性，这归因于抑制Cd吸收与CuO NPs粘附在根际表面以抑制Cd ²⁺流入有关，下调一些关键的 Cd 转运基因（Nramp5和HMA2)，以及增强抗氧化能力（SOD、POD 和 CAT）和上调 ROS 清除相关基因。此外，CuO NP 预处理对 Cd 转运蛋白和 ROS 清除相关基因的调控在水稻和大麦之间表现出微小差异，这可能是它们对 Cd 胁迫和 CuO NP 预处理的响应差异的原因。 . 可以得出结论，低浓度的 CuO NPs 可减轻植物中作为纳米级保护剂的 Cd 毒性，并提供对抗 Cd 污染的替代方法。