Department of Biology, Kline Biology Tower, Yale University, 06511, New Haven, CT, USA.
Planta. 1983 Nov;159(3):231-7. doi: 10.1007/BF00397530.
We have compared the effects of the auxin, indole-3-acetic acid (IAA) with that of other weak acids on the plasma-membrane potential of oat (Avena sativa L.) coleoptile cells. Cells treated with 1 μM IAA at pH 6 depolarize 20-25 mV in 10-12 min, but they then repolarize, until by 20-25 min their potentials are about 25 mV more negative than the initial value. Similar concentrations of benzoic and butyric acids cause the initial depolarization, but not the subsequent hyperpolarization. The hyperpolarization is therefore specific to IAA. All the weak acids, including IAA, evoke a rapid hyperpolarization when their concentrations are raised to 10 mM. This result indicates that at high concentrations, the uptake of undissociated weak acids activates electrogenic proton pumping, most likely by lowering cytoplasmic pH. In contrast, the hyperpolarization observed with concentrations of IAA four orders of magnitude lower appears to be a specific hormonal effect. This specific, auxin-induced hyperpolarization occurs at the same time as the initiation of net proton secretion and supports the hypothesis that auxin initiates extension growth by increasing proton pumping.
我们比较了生长素吲哚乙酸（IAA）与其他弱酸对燕麦（Avena sativa L.）胚芽鞘细胞质膜电位的影响。在 pH 值为 6 时，用 1μM IAA 处理细胞会在 10-12 分钟内去极化 20-25mV，但随后会复极化，直到 20-25 分钟后，其电位比初始值负 25mV 左右。类似浓度的苯甲酸和丁酸会引起初始去极化，但不会引起随后的超极化。因此，超极化是 IAA 特有的。所有弱酸，包括 IAA，当其浓度升高到 10mM 时，都会引起快速超极化。这一结果表明，在高浓度下，未解离弱酸的摄取会激活电致质子泵，很可能是通过降低细胞质 pH 值。相比之下，在 IAA 浓度低四个数量级时观察到的超极化似乎是一种特定的激素效应。这种特定的、由生长素诱导的超极化发生在净质子分泌开始的同时，支持了生长素通过增加质子泵来启动延伸生长的假说。
