Biological Nitrification Inhibition (BNI) of Brachiaria humidicola has been attributed to nitrification-inhibiting fusicoccanes, most prominently 3-epi-brachialactone. However, its release mechanism from B. humidicola roots remains elusive. Two hydroponic experiments were performed to investigate the role of rhizosphere pH and nutritional N form in regulating 3-epi-brachialactone release by B. humidicola and verify the underlying release pathway. Low rhizosphere pH and NH4 + nutrition promoted 3-epi-brachialactone exudation. However, the substitution of NH4 + by K+ revealed that the NH4 + effect was not founded in a direct physiological response to the N form but was related to the cation-anion balance during nutrient uptake. Release of 3-epi-brachialactone correlated with the transmembrane proton gradient ΔpH and NH4 + uptake (R2 = 0.92 for high ~ 6.8 and R2 = 0.84 for low ~ 4.2 trap solution pH). This corroborated the release of 3-epi-brachialactone through secondary transport, with the proton motive force (ΔP) defining transport rates across the plasma membrane. It was concluded that 3-epi-brachialactone release cannot be conceptualized as a regulated response to soil pH or NH4 + availability, but merely as the result of associated changes in ΔP.

中文翻译：

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根际 pH 值和阳离子-阴离子平衡决定硝化抑制剂 3-epi-臂内酯的渗出，表明通过二级转运释放

Brachiaria weticola 的生物硝化抑制 (BNI) 归因于抑制硝化的褐藻，最突出的是 3-epi-brachialactone。然而，其从 B.hydricola 根部的释放机制仍然难以捉摸。进行了两个水培实验以研究根际 pH 值和营养氮形式在调节 B. weticola 释放 3-epi-brachialactone 中的作用并验证潜在的释放途径。低根际 pH 值和 NH4 + 营养促进 3-epi-臂内酯渗出。然而，NH4+ 被 K+ 取代表明 NH4+ 效应不是建立在对 N 形式的直接生理反应中，而是与养分吸收过程中的阳离子-阴离子平衡有关。3-epi-臂内酯的释放与跨膜质子梯度 ΔpH 和 NH4 + 吸收（R2 = 0. 92 高 ~ 6.8 和 R2 = 0.84 低 ~ 4.2 陷阱溶液 pH 值）。这证实了 3-epi-臂内酯通过二次转运的释放，质子动力 (ΔP) 定义了跨质膜的转运速率。得出的结论是，不能将 3-epi-臂内酯释放概念化为对土壤 pH 值或 NH4 + 有效性的调节响应，而仅仅是 ΔP 相关变化的结果。