Brownlee C, Kendrick R E
Department of Plant Biology, The University, Newcastle upon Tyne, NE1 7RU, United Kingdom.
Plant Physiol. 1979 Aug;64(2):206-10. doi: 10.1104/pp.64.2.206.
K(+) [(86)Rb(+)] uptake by Phaseolus aureus Roxb. hypocotyl segments cut immediately below the hook is inhibited by the active form of phytochrome (Pfr). Short load-short wash experiments indicate that the inhibition of uptake occurs across the plasmalemma. A maximal inhibition of short term uptake occurs in 10 to 50 millimolar KCI. Low temperature had only a small effect on influx and the inhibition of influx from 50 millimolar KCI. A consideration of the electrochemical gradient for K(+) suggests that passive K(+) fluxes may predominate under these conditions. Red light induces small depolarizations of membrane potential in subhook cells. Far red light antagonizes this effect. Pfr inhibits efflux of K(+)[(86)Rb(+)] from subhook segments. This effect is also relatively insensitive to low temperature. This inhibition of efflux may reflect inhibition of a K(+) -K(+) exchange process, or reduced passive permeability of the plasmalemma to K(+). In contrast, Pfr enhances short term uptake of K(+)[(86)Rb(+)] in apical hypocotyl hook segments of Phaseolus aureus Roxb. Short load-short wash experiments indicate that fluxes across the plasmalemma are modified by Pfr. A maximal enhancement of short term influx occurs in 50 millimolar KCI. Influx and the red light enhancement of influx from 50 millimolar KCI are relatively insensitive to low temperature. Pfr also enhances efflux of K(+)[(86)Rb(+)] from preloaded apical hook segments. This increased influx may reflect enhancement of a K(+) -K(+) exchange process or increased passive permeability of the plasmalemma to K(+).
菜豆下胚轴钩状部位下方紧邻处切下的切段对K(+) [(86)Rb(+)] 的吸收受到光敏色素（Pfr）活性形式的抑制。短时间加载 - 短时间冲洗实验表明，吸收的抑制发生在质膜上。在10至50毫摩尔氯化钾中，短期吸收受到最大抑制。低温对流入量以及来自50毫摩尔氯化钾的流入抑制只有很小的影响。考虑到K(+)的电化学梯度表明，在这些条件下被动K(+)通量可能占主导。红光诱导钩状部位下方细胞的膜电位发生小的去极化。远红光拮抗这种效应。Pfr抑制K(+) [(86)Rb(+)] 从钩状部位下方切段流出。这种效应也相对不受低温影响。这种流出抑制可能反映了对K(+) -K(+)交换过程的抑制，或者质膜对K(+)的被动通透性降低。相比之下，Pfr增强了菜豆下胚轴顶端钩状部位切段对K(+) [(86)Rb(+)] 的短期吸收。短时间加载 - 短时间冲洗实验表明，质膜上的通量受到Pfr的影响。在50毫摩尔氯化钾中，短期流入量得到最大增强。来自50毫摩尔氯化钾的流入量以及红光对流入量的增强相对不受低温影响。Pfr还增强了预先加载的顶端钩状部位切段中K(+) [(86)Rb(+)] 的流出。这种流入增加可能反映了K(+) -K(+)交换过程的增强或质膜对K(+)的被动通透性增加。
