Department of Botany, University of California, Davis, California 95616.
Plant Physiol. 1984 Jan;74(1):61-6. doi: 10.1104/pp.74.1.61.
Electrophysiological measurements on internodal cells of Chara corallina Klein ex Willd., em. R.D.W. revealed that in the presence of (2-[4-(2',4'-dichlorophenoxy)phenoxy]propionic acid) (diclofop) the membrane potential was very sensitive to the pH of the bathing medium. At pH 5.7, 100 micromolar diclofop caused a slow reduction in the electrogenic component of the membrane potential to the value of -123 +/- 5 millivolts. Membrane resistance initially decreased, recovered transiently, then stabilized at approximately 65% of the control value. At pH 7.0, the potential appeared to plateau around -200 millivolts before rapidly declining to -140 +/- 4 millivolts; removal of diclofop resulted in recovery of the electrogenic component. Diclofop reduced cytoplasmic ATP levels by 96.4% and 36.6% at pH 5.7 and 7.0, respectively. At pH 8.2, diclofop did not change the ATP concentration significantly, but induced a hyperpolarization of the membrane potential to near -250 millivolts, and also reduced or inhibited the dark-induced hyperpolarization; the light-induced depolarization was reduced to a lesser extent. DCMU applied in the light elicited the same response at the plasmalemma as placing cells in the dark. When K(+) channels were opened and cells depolarized with 10 millimolar K(+), diclofop induced a further depolarization of approximately 30 millivolts. Cells decoupled with HPO(4) (-2) were still sensitive to diclofop. Currents associated with OH(-) efflux and HCO(3) (-) influx, as measured with a vibrating probe technique, became spatially destabilized and reduced in magnitude in the presence of diclofop. After 60 minutes, most of the cell surface was engaged in a low level of OH(-) efflux activity. The results indicate that diclofop may be a proton ionophore at pH 7.0 and 5.7. At pH 8.2, diclofop may inhibit the operation of the H(+)-ATPase and OH(-) efflux systems associated with HCO(3) (-) transport by perturbing the control processes that integrate the two, without a reduction in ATP concentration.
用电生理学方法对小立碗藓(Chara corallina Klein ex Willd., em. R.D.W.)的居间细胞进行研究,结果表明,在 2-[4-(2',4'-二氯苯氧基)苯氧基]丙酸(diclofop)存在的情况下,细胞膜电位对浴液的 pH 值非常敏感。在 pH 值为 5.7 时,100 微摩尔的 diclofop 会使细胞膜的电动势中的生电分量缓慢降低到-123 +/- 5 毫伏。细胞膜电阻最初下降,然后短暂恢复,然后稳定在对照值的约 65%。在 pH 值为 7.0 时,电位似乎在迅速下降到-140 +/- 4 毫伏之前在约-200 毫伏处达到平台;去除 diclofop 后,生电分量恢复。Diclofop 将细胞质中的 ATP 水平分别降低了 96.4%和 36.6%,在 pH 值为 5.7 和 7.0 时。在 pH 值为 8.2 时,diclofop 并没有显著改变 ATP 浓度,但会使细胞膜电位发生超极化,接近-250 毫伏,并降低或抑制暗诱导的超极化;光诱导的去极化程度则较小。在光下应用 DCMU 会在质膜上引起与将细胞置于黑暗中相同的反应。当 K(+)通道打开并且细胞用 10 毫摩尔 K(+)去极化时,diclofop 会引起约 30 毫伏的进一步去极化。用 HPO(4) (-2)去耦的细胞仍然对 diclofop 敏感。用振动探针技术测量的与 OH(-)外排和 HCO(3) (-)内流相关的电流在 diclofop 存在时变得空间不稳定并且幅度降低。60 分钟后,大部分细胞表面都参与了低水平的 OH(-)外排活性。结果表明,在 pH 值为 7.0 和 5.7 时,diclofop 可能是质子载体。在 pH 值为 8.2 时,diclofop 可能通过扰乱整合两者的控制过程来抑制与 HCO(3) (-)转运相关的 H(+)-ATP 酶和 OH(-)外排系统的运作,而不会降低 ATP 浓度。