Natural organic matter (NOM) affects the environmental behaviors of AgNPs, which may change their phytotoxicity to plants. However, more evidence can be provided to illustrate how NOM influences AgNPs-induced phytotoxicity. In this study, using rice (Oryza sativa) as a model, the effects of NOM, Suwannee River humic acid (SRHA) and fulvic acid (FA), on the dissolution and phytotoxicity of AgNPs were investigated. Silver ions decreased in both AgNPs and AgNO₃ solution in the presence of NOM, and the effect of SRHA was stronger than FA. Image-XRF (iXRF) results showed that Ag mainly remained in the root rather than the shoot of rice seedling exposed to AgNPs. NOM mitigated the negative effects of AgNPs and AgNO₃ on rice with lower germination inhibition rate, less chlorophyll reduction, more relative biomass and less O₂^•− content. Moreover, NOM improved root cell viability according to FDA fluorescent dye as well as maintained the normal root morphology. Interestingly, the neutral sugars content from pectin, hemicellulose 1, hemicellulose 2 and cellulose of root cell wall in AgNPs and AgNO₃ treatments differed from the control, while it was close to the regular content in AgNPs/AgNO₃+SRHA/FA groups, which implied that NOM regulated the changes. Besides, SRHA led to less germination and less relative biomass than FA due to different chemical characters. Thus, NOM needs to be considered when studying the phytotoxicity of AgNPs.

天然有机物（NOM）影响AgNP的环境行为，这可能会改变其对植物的植物毒性。但是，可以提供更多证据说明NOM如何影响AgNPs诱导的植物毒性。本研究以水稻（Oryza sativa）为模型，研究了NOM，Suwannee River腐殖酸（SRHA）和黄腐酸（FA）对AgNPs的溶出度和植物毒性的影响。在存在NOM的情况下，AgNPs和AgNO ₃溶液中的银离子均减少，并且SRHA的作用强于FA。图像XRF（iXRF）结果表明，Ag主要残留在根中，而不是暴露于AgNPs的水稻幼苗的嫩芽。NOM减轻了AgNP和AgNO ₃的负面影响抑制发芽率低，叶绿素还原减少，相对生物量更多，O ₂ ^•−含量更低的水稻。此外，根据FDA荧光染料的规定，NOM改善了根细胞的活力，并保持了正常的根形态。有趣的是，AgNPs和AgNO ₃处理中果胶，半纤维素1，半纤维素2和根细胞壁纤维素中的中性糖含量与对照相比有所不同，但接近AgNPs / AgNO ₃ + SRHA / FA组中的常规含量，这暗示NOM会控制变更。此外，由于不同的化学特性，SRHA的发芽率和相对生物量均低于FA。因此，在研究AgNPs的植物毒性时需要考虑NOM。