Although the ability of humic (HA) and fulvic acids (FA) to improve plant growth has been demonstrated, knowledge about the mechanisms responsible for the direct effects of HA and FA on the promotion of plant growth is scarce and fragmentary. Our study investigated the causal role of both root PM H⁺‐ATPase activity and ABA in the SHA‐promoting action on both root and shoot growth. The involvement of these processes in the regulation of shoot cytokinin concentration and activity was also studied. Our aim was to integrate such plant responses for providing new insights to the current model on the mode of action of HA for promoting root and shoot growth. Experiments employing specific inhibitors and using Cucumis sativus L. plants show that both the root PM H⁺‐ATPase activity and root ABA play a crucial role in the root growth‐promoting action of SHA. With regard to the HA‐promoting effects on shoot growth, two pathways of events triggered by the interaction of SHA with plant roots are essential for the increase in root PM H⁺‐ATPase activity—which also mediates an increase in cytokinin concentration and action in the shoot—and the ABA‐mediated increase in hydraulic conductivity (Lp_r).

中文翻译：

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根 ABA 和 H+-ATP 酶是腐殖酸促进根和芽生长的关键因素。

尽管腐殖酸 (HA) 和黄腐酸 (FA) 改善植物生长的能力已被证明，但有关 HA 和 FA 对促进植物生长的直接影响的机制的了解却很少且不完整。我们的研究调查了根 PM H ⁺ ATP 酶活性和 ABA 在根和芽生长的 SHA 促进作用中的因果作用。还研究了这些过程在芽细胞分裂素浓度和活性调节中的参与。我们的目标是整合这些植物反应，为当前关于 HA 促进根和芽生长的作用模式的模型提供新的见解。使用特定抑制剂和使用黄瓜植物的实验表明，根部 PM H ⁺ ATP 酶活性和根部 ABA 在 SHA 的根部生长促进作用中发挥着至关重要的作用。关于 HA 对芽生长的促进作用，由 SHA 与植物根相互作用触发的两个事件途径对于根 PM H + ATP 酶活性的增加至关重要，这也介导细胞分裂素浓度和作用^的增加芽——以及 ABA 介导的水力传导率 (Lp _r ) 的增加。