Luan Hongwei, Hu Huidi, Li Wei, Liu Zhilei, Liu Xuesheng, Zhang Xihai, Li Sha
College of Electrical Engineering and Information, Northeast Agricultural University, Harbin, 150030, China.
College of Agriculture, Northeast Agricultural University, Harbin, 150030, China.
BMC Plant Biol. 2025 Jul 22;25(1):944. doi: 10.1186/s12870-025-07004-9.
The mechanism of nitrate inhibiting soybean (Glycine max L. Merr.) nodulation and nitrogen fixation is still controversial. The aim of this study was to evaluate whether increased carbon allocation could mitigate the inhibitory effect of indirectly supplied nitrate on nodule nitrogen fixation METHODS: In this study, dual-root soybean plants were constructed with one side nodulated and the other side non-nodulated. Nitrate was applied to the non-nodulated lateral roots, either directly or following the girdling of the base of the non-nodulated root, to enhance carbon transport from the shoot o the nodulated side. After 2 days and 7 days of treatment, the nitrogen fixation capacity was assessed, nodule ultrastructure was examined, and the concentrations of sucrose, starch, and soluble sugars in roots and nodules on both sides were determined.
Indirect nitrate supply significantly suppressed nodulation and nitrogen fixation, reduced sucrose and starch concentrations in nodules, and induced premature senescence of nodule structure. Enhancing carbon allocation to the nodules increase sucrose and starch levels, restored the integrity of the infected cell wall and peribacteroid membrane, and improved nitrogenase activity.
Increasing carbon distribution to nodules can restore the structural integrity of infected cells and alleviate the negative impact of indirect nitrate supply on soybean nitrogen fixation.
硝酸盐抑制大豆（Glycine max L. Merr.）结瘤和固氮的机制仍存在争议。本研究的目的是评估增加碳分配是否可以减轻间接供应硝酸盐对根瘤固氮的抑制作用。方法：在本研究中，构建了双根大豆植株，一侧结瘤而另一侧不结瘤。将硝酸盐施用于未结瘤的侧根，要么直接施用，要么在未结瘤根基部环割后施用，以增强碳从地上部向结瘤侧的运输。处理2天和7天后，评估固氮能力，检查根瘤超微结构，并测定两侧根和根瘤中蔗糖、淀粉和可溶性糖的浓度。
间接供应硝酸盐显著抑制结瘤和固氮，降低根瘤中蔗糖和淀粉浓度，并诱导根瘤结构过早衰老。增加向根瘤的碳分配提高了蔗糖和淀粉水平，恢复了受感染细胞壁和类菌体周膜的完整性，并提高了固氮酶活性。
增加向根瘤的碳分配可以恢复受感染细胞的结构完整性，并减轻间接供应硝酸盐对大豆固氮的负面影响。
