Department of Botany, University of Illinois, Urbana, Illinois 61801.
Plant Physiol. 1977 May;59(5):1004-7. doi: 10.1104/pp.59.5.1004.
Acid-induced growth was compared to auxin-induced growth. After a transient pH 4-induced increase in the elongation rate was completed, auxin could still induce an enhanced rate of elongation in soybean (Glycine max) hypocotyl segments. This auxin response occurred both when the medium was changed to pH 6 before auxin addition, and when the auxin was added directly to the pH 4 medium. This postacid response to auxin was persistent, and quite unlike a postacid response to acid, which was again shortlived. One mm N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (pH 7) inhibited the first response to auxin (the first response to auxin being similar to the acid response), but not the second response. This did not appear to be simply a hydrogen ion neutralizing effect, however, since a 50-fold increase in buffer concentration at pH 6 did not inhibit the first response. Decrease in the pH of the external medium, previously shown to occur with excised soybean hypocotyl segments, was not affected by auxin. Furthermore, this pH drop, during which the cells appear to be adjusting their external pH to about 5.4, did not result in an increased rate of elongation. Addition of auxin after the equilibrium pH had been attained did not alter the pH, but it did increase the rate of elongation, eliciting a normal auxin response. It was concluded that hydrogen ions do not mediate in long term auxin-induced elongation in soybean hypocotyl.
酸诱导的生长与生长素诱导的生长进行了比较。在短暂的 pH4 诱导伸长率增加完成后，生长素仍然可以在大豆（Glycine max）下胚轴节段中诱导增强的伸长率。这种生长素反应既发生在添加生长素之前将培养基的 pH 值改变为 6 时，也发生在将生长素直接添加到 pH4 培养基中时。这种对生长素的后酸化反应是持久的，与对酸的后酸化反应完全不同，后者是短暂的。1mm N-2-羟乙基哌嗪-N'-2-乙磺酸（pH7）抑制了对生长素的第一次反应（第一次对生长素的反应类似于对酸的反应），但不抑制第二次反应。然而，这似乎不是简单的氢离子中和效应，因为在 pH6 时缓冲液浓度增加 50 倍并不抑制第一次反应。先前在离体大豆下胚轴节段中显示的外部介质 pH 值降低不受生长素的影响。此外，在细胞似乎将其外部 pH 值调整到约 5.4 的过程中，这种 pH 下降不会导致伸长率增加。在达到平衡 pH 值后添加生长素不会改变 pH 值，但会增加伸长率，引发正常的生长素反应。因此，结论是氢离子不会介导大豆下胚轴中生长素诱导的长期伸长。
