Abstract: 【Objective】Molybdenum (Mo) serves as an essential active component of nitrate reductase, playing a pivotal role in the reduction of nitrate nitrogen and nitrogen metabolism. This study aims to investigate the relationship between nano-MoO₃ and rice root morphology, organic acid secretion, and nitrate absorption, laying a theoretical basis for improving nitrate nitrogen absorption and utilization in rice through novel nano-fertilizers. 【Method】Using Nanjing 9108 rice as the research material, hydroponic experiments with nitrate nitrogen as the nitrogen source were conducted with treatments of no Mo application (Mo concentration, 0 μg/L), sodium molybdate (50, 100, 200, 400 μg/L), and nano-MoO₃ (50, 100, 200, 400 μg/L). Differences in rice root morphology, root-secreted organic acid, and nitrogen content were analyzed. 【Results】Exogenous Mo significantly increased rice root dry weight, total root length, root volume, total root surface area, total absorption area, and active absorption area, significantly optimizing rice root morphology compared to the no Mo treatment. At the same Mo application rates, nano-MoO₃ treatments showed significantly higher enhancement effects than sodium molybdate treatments. Root oxidation and reduction capacities, as well as organic acid secretion, increased significantly in response to exogenous Mo treatments, indicating enhanced root physiological activity. As Mo concentrations increased, the root oxidation and reduction capacities under sodium molybdate treatments initially increased and then decreased. Except for acetic acid, there were no differences in the secretion of malic acid, tartaric acid, succinic acid, citric acid, and oxalic acid at various sodium molybdate concentrations. However, both root oxidation/reduction capacities and organic acid secretion in nano-MoO₃ treatments increased with rising application rates. Factor analysis and redundancy analysis results indicated that rice root morphological indicators, root redox capacities, and organic acid secretion were positively correlated with root nitrogen content. Exogenous Mo addition promoted nitrate nitrogen absorption by rice roots through improvements in root morphological and physiological traits. 【Conclusion】Exogenous Mo enhanced rice root morphological and physiological activities by increasing root length, root surface area, redox capacities, and organic acid secretion, thereby promoting nitrate nitrogen absorption. Nano-MoO₃ demonstrated superior promotional effects compared to sodium molybdate at the same Mo application rates. In agricultural production, appropriate Mo fertilizer addition, especially nano-MoO₃ fertilizer, can improve rice root morphological and physiological functions, enhancing nitrate nitrogen absorption and utilization.

Key words: nano-molybdenum, rice, root morphology, root redox capacity, root exudates, nitrate nitrogen

摘要： 【目的】钼是硝酸还原酶的活性组分，在硝态氮的还原和氮素代谢过程中具有核心作用。探究纳米钼对水稻根系形态、有机酸分泌及其与硝态氮吸收的关系，有望为新型纳米肥料提高水稻硝态氮吸收利用提供理论依据。【方法】以南粳9108为研究对象，以硝态氮为氮源的水培实验设置不施钼 (0 μg/L)、钼酸钠组(50、100、200、400 μg/L)和纳米钼组(50、100、200、400 μg/L)处理， 分析水稻根系形态、根系分泌有机酸和氮含量等的差异。【结果】外源钼显著增加了水稻根干质量、总根长、根体积、根总表面积、总吸收面积和活跃吸收面积，较不施钼处理显著优化了水稻根系形态。在相同钼添加量条件下，纳米钼处理效果显著高于钼酸钠处理。外源钼处理的根系氧化力和还原力、有机酸分泌量均显著增加，根系生理活动增强；随着钼添加量增加， 钼酸钠处理组根系氧化力和还原力呈先增加后下降趋势，除乙酸外，苹果酸、酒石酸、琥珀酸、柠檬酸和草酸含量不同钼浓度处理间无差异；纳米钼处理的根系氧化力、还原力和有机酸量均随施用量的增加而增加。因子分析和冗余分析结果表明，水稻根系形态指标、根系氧化还原力及有机酸分泌量与根系氮含量正相关，外源钼添加通过改善水稻根系形态和生理特征促进水稻根系对硝态氮的吸收。【结论】外源钼通过增加水稻根长、根表面积、有机酸分泌量，增强根系氧化还原能力，改善了根系形态生理活性，进而增加了水稻根系对硝态氮的吸收。相同钼施用量条件下，纳米钼的促进效果优于钼酸钠。生产上可以通过适当添加钼肥特别是纳米钼肥来改善水稻根系形态及生理功能，增强水稻根系对硝态氮的吸收和利用。

关键词: 纳米钼, 水稻, 根系形态, 根系氧化还原能力, 根系分泌物, 硝态氮