Cadmium (Cd) toxicity negatively impacts plant health and productivity. Nanosilica (SiO₂NPs) and salicylic acid (SA) enhance plant performance and alleviate heavy metals stress. Yet, their combined effects against Cd-toxicity in rice remained less-explored. Thus, a hydroponic study investigated the individual and combined effects of SiO₂NPs and SA on Cd-stress mitigation in rice at physio-biochemical, cellular, and molecular levels. Results indicated that Cd-alone treatment caused a significant reduction in rice growth and biomass and photosynthetic efficiency, which was associated with oxidative damage caused by enhanced Cd-accumulation in plant tissues. Cd-induction also potentiated its phytotoxicity by triggering enzymatic antioxidants against the extra production of reactive oxygen species (ROS). The addition of SiO₂NPs and/or SA markedly minimized the Cd-induced toxicity by reducing Cd-bioaccumulation (42‒56%), protecting photosynthetic efficiency, which were directly correlated with seedling biomass and restored cellular structures (leaf ultrastructure and surface morphology). The combined application of SiO₂NPs and SA was more effective in activating antioxidant enzymes, phytohormones biosynthesis, and reducing oxidative damages caused by Cd than sole application. This was evident in the decreased production of ROS, malondialdehyde contents (29‒37%), and recovered membrane stability. Moreover, SiO₂NPs and/or SA relieved Cd-bioaccumulation (41‒56%) by downregulating the Cd-related transporter genes (OsNramp1, OsNramp5, OsHMA2, and OsHMA3). Altogether, the cellular Cd-accumulation, photosynthesis, antioxidant defense, and phytohormones against oxidative stress can be ideal markers for cultivating rice in Cd-contaminated soils.

中文翻译：

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纳米二氧化硅和水杨酸协同调节水稻中镉的毒性


镉 （Cd） 毒性会对植物健康和生产力产生负面影响。纳米二氧化硅 （SiO₂NPs） 和水杨酸 （SA） 可增强植物性能并缓解重金属胁迫。然而，它们对水稻中 Cd 毒性的综合作用仍然较少被探索。因此，一项水培研究调查了 SiO₂NPs 和 SA 在生理生化、细胞和分子水平上对水稻 Cd 应激缓解的单独和综合影响。结果表明，单独使用 Cd 处理导致水稻生长、生物量和光合效率显著降低，这与植物组织中 Cd 积累增强引起的氧化损伤有关。镉诱导还通过触发酶促抗氧化剂来对抗活性氧 （ROS） 的额外产生，从而增强了其植物毒性。SiO₂NPs 和/或 SA 的添加通过减少 Cd 生物积累 （42\u201256%） 显着降低了 Cd 诱导的毒性，保护了光合效率，这与幼苗生物量和恢复的细胞结构（叶片超微结构和表面形态）直接相关。SiO₂NPs 和 SA 的联合应用比单独应用更有效地激活抗氧化酶、植物激素生物合成和减少 Cd 引起的氧化损伤。这在 ROS 的产生、丙二醛含量 （29\u201237%） 和膜稳定性的恢复中很明显。此外，SiO₂NPs 和/或 SA 通过下调 Cd 相关转运蛋白基因 （OsNramp1、OsNramp5、OsHMA2 和 OsHMA3） 来缓解 Cd-生物积累 （41\u201256%）。 总而言之，细胞 Cd积累、光合作用、抗氧化防御和抵抗氧化应激的植物激素可以成为在受 Cd污染的土壤中种植水稻的理想标志物。