The application of selenium nanoparticles (Se NPs) in agriculture has garnered significant attention, yet there remains a knowledge gap regarding the correlation between the size of Se NPs and their availability in soil. To address this gap, adsorption experiments, soil column experiments, and pot experiments were conducted to investigate the relationship between the availability in soil of Se NPs and their particle size. The results showed that the adsorption capacities of Se NPs with various sizes (30, 50, 80, 110 nm) to fulvic acid (FA) was decreased with increasing particle sizes and pH. Small sized Se NPs (30 nm) are more stable because they adsorb more organic matter, which significantly decreases aggregation. Moreover, the mobility of Se NPs was decreased by increasing clay content in soil and particle size. These results demonstrated that small-sized Se NPs have higher bioavailability than large-sized Se NPs. The Se content in rhizosphere soil and shoot was significantly increased by 319.4% and 220.2% upon exposure to Se NPs (30 nm), higher than that for others (50, 80, 110 nm and 2 µm). The reason is that small-sized Se NPs are more stable in the soil, more easily migrate from the non-rhizosphere to the rhizosphere and interact with crop roots, leading to increased root exudations. These interactions recruit beneficial microorganisms in the rhizosphere. In turn, the improved root exudations and the presence of these microorganisms enhance the bioavailability of Se NPs. Linear regression analysis indicated that the size of soil-applied Se NPs should fall within the range of 11–631 nm, as those outside of this range may not meet the standard for Se-enriched food. Besides, the nutrient accumulation in leaves promoted photosynthesis (81.1%) and increased the yield (113.1%) of by small-sized Se NPs (30 nm). Therefore, these information highlights the critical role of Se NPs size in crop Se biofortification for agriculture production.

中文翻译：

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土壤和植物中硒纳米粒子的生物利用度：粒径的作用

硒纳米颗粒（Se NPs）在农业中的应用引起了人们的广泛关注，但对于硒纳米颗粒的尺寸与其在土壤中的可用性之间的相关性仍然存在知识差距。为了解决这一问题，我们进行了吸附实验、土柱实验和盆栽实验，以研究土壤中硒纳米粒子的有效性与其粒径之间的关系。结果表明，不同粒径（30、50、80、110 nm）的Se NPs对黄腐酸（FA）的吸附能力随着粒径和pH值的增加而降低。小尺寸的 Se NP（30 nm）更稳定，因为它们吸附更多的有机物，从而显着减少聚集。此外，随着土壤中粘土含量和粒径的增加，Se NPs 的迁移率降低。这些结果表明，小尺寸的 Se NPs 比大尺寸的 Se NPs 具有更高的生物利用度。暴露于Se NPs (30 nm)后，根际土壤和地上部的Se含量显着增加了319.4%和220.2%，高于其他溶液(50、80、110 nm和2 µm)。原因是小尺寸的硒纳米颗粒在土壤中更稳定，更容易从非根际迁移到根际并与作物根部相互作用，导致根系分泌物增加。这些相互作用在根际招募有益微生物。反过来，根系分泌物的改善和这些微生物的存在增强了 Se NP 的生物利用度。线性回归分析表明，土壤施用的纳米硒颗粒的粒径应在11-631 nm范围内，超出此范围的纳米颗粒可能不符合富硒食品的标准。此外，叶片中养分的积累促进了光合作用（81.1%），并提高了小尺寸Se NPs（30 nm）的产量（113.1%）。因此，这些信息强调了硒纳米颗粒尺寸在农业生产作物硒生物强化中的关键作用。