The use of plant-based biostimulants to increase crop yield and enhance protection has grown in popularity. We previously manufactured an inoculant combining humic acids with plant growth-promoting bacteria and observed a significant effect on crop yields. However, electrophysiology studies elucidating the mechanisms responsible for enhanced nutrient and water uptake are scarce and are generally restricted to in vitro models. In this study, a suspension of humic acids isolated from vermicompost along with Herbaspirillum seropedicae was applied to maize seedlings. We measured the root H+ flux with an ion-selective vibrating probe system. Furthermore, the transcription of plasma membrane H+ ATPase, aquaporin and high- or low-affinity nitrate transporters was measured. Inoculation activated the extracellular H+ flux, thus changing the pH and membrane potential of maize root cells and altering the electrochemical potential generated by P–H+-ATPase at the biochemical and molecular level. The overexpression of aquaporins was also observed; however, nitrate transporters were repressed by the inoculants. We demonstrate an increase in the H+ efflux in maize root seedlings inoculated with H. seropedicae and concomitant changes in membrane voltage. The inoculation of H. seropedicae in the presence of humic acids decreased the H+ flux and surface acidification without changes in the aquaporin transcription level. However, the H+ flux in root seedlings in inoculated plants (with or without humic acids) was larger in respect to control plants. These results support the increased water and nitrogen efficiency in plants inoculated with humic acids and H. seropedicae.

中文翻译：

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腐植酸和草螺旋藻改变玉米根苗细胞外H ⁺通量和基因表达

使用基于植物的生物刺激剂来增加农作物产量并增强保护作用已日益普及。我们以前制造了将腐殖酸与植物生长细菌结合的孕育剂，并观察到了对作物产量的显着影响。然而，电生理研究阐明了增加营养和水吸收的机制，这是稀缺的，并且通常仅限于体外模型。在这项研究中，将从ver麦中分离出的腐殖酸悬浮液与草状螺旋藻一起用于玉米幼苗。我们用离子选择性振动探针系统测量了根H +通量。此外，测量了质膜H + ATPase，水通道蛋白和高或低亲和力硝酸盐转运蛋白的转录。接种激活了细胞外H +通量，因此，改变了玉米根细胞的pH值和膜电位，并在生化和分子水平上改变了PH + ATPase产生的电化学电位。还观察到水通道蛋白的过度表达。然而，接种剂抑制了硝酸盐转运蛋白。我们证明了接种H. seropedicae的玉米根苗中H +外排量增加，并伴随着膜电压的变化。在腐殖酸的存在下接种蛇形双歧杆菌减少了H +通量和表面酸化，而水通道蛋白的转录水平却没有变化。但是，相对于对照植物，接种植物（有或没有腐殖酸）根苗中的H +通量更大。这些结果支持了接种腐殖酸和蛇形双歧杆菌的植物中提高的水和氮效率。