Department of Pure and Applied Sciences, College of Arts and Sciences, University of Tokyo, Tokyo 153.
Plant Physiol. 1985 Nov;79(3):825-8. doi: 10.1104/pp.79.3.825.
The light-dependent pH changes in the suspending medium of guard cell protoplasts (GCP) from Vicia faba were studied. Upon illumination, the medium was initially slightly alkalinized and then acidified. The extent of alkalinization was lower in CO(2)-free air than in normal air. This initial alkalinization was inhibited by DCMU. Acidification in CO(2)-free air became observable in shorter duration of light exposure than that in normal air. The rate of acidification was higher in CO(2)-free air than in normal air. The CO(2) level of the medium decreased in the light, and increased in the dark. (14)CO(2) uptake was enhanced 2- to 3-fold by light, but not in the presence of DCMU. These results indicate that photosynthetic CO(2) fixation does take place in GCP and that the initial alkalinization is due to this photosynthetic CO(2) uptake. Diethylstilbestrol, a nonmitochondrial membrane-bound ATPase inhibitor, inhibited the acidification, suggesting that the acidification resulted from H(+) extrusion by GCP. The acidification in light was also prevented by KCN, and partly by DCMU. Possible mechanisms of alkalinization and acidification are discussed in relation to guard cell metabolism.
我们研究了蚕豆保卫细胞原生质体悬浮液在依赖光照时的 pH 值变化。照光后，介质最初略有碱化，然后酸化。在无 CO2 的空气中，碱化程度比在正常空气中低。这种初始的碱化作用被 DCMU 抑制。在无 CO2 的空气中，光暴露时间较短时即可观察到酸化，而在正常空气中则需要较长时间。无 CO2 的空气中的酸化速度比正常空气中快。光照下介质中的 CO2 水平下降，黑暗中上升。（14）CO2 摄取在光照下增强了 2-3 倍，但在 DCMU 存在下则没有。这些结果表明，光合作用 CO2 固定确实发生在 GCP 中，而初始碱化是由于这种光合作用 CO2 摄取。非线粒体膜结合型 ATP 酶抑制剂己烯雌酚抑制了酸化，表明酸化是由 GCP 排出 H+引起的。KCN 和部分 DCMU 也能阻止光照下的酸化。讨论了与保卫细胞代谢有关的碱化和酸化的可能机制。
