Abstract—

Illuminated giant cells of characean algae exhibit membrane excitability as well as the spatial patterns of photosynthesis and transmembrane H⁺ fluxes. The excitation of plasmalemma under these conditions results in the transient degradation of external alkaline and acid zones and inhibits photosynthesis in the alkaline zones. The generation of action potential in the patterned internodes is followed by cell hyperpolarization that peaks in 1 min and lasts up to 15 min. In order to exclude the influence of drifting resting potential on the chloroplast response to plasma membrane excitation, the voltage clamp mode was applied in this work, and chlorophyll fluorescence changes caused by a short depolarizing pulse were monitored. The depolarizing shift of membrane potential under voltage clamp conditions was found to induce a large depression of \(F_{{\text{m}}}^{{{'}}}\) chlorophyll fluorescence and photosynthetic activity, provided that inward Ca²⁺ and Cl^– currents were triggered and that a steady-state inward H⁺ flux (or OH^– efflux) persisted before the application of an electric stimulus. The depolarization-induced ion currents measured in the alkaline and acidic cell regions under light and in darkness were found to differ significantly. The results are consistent with the notion that the massive inward H⁺ flow occurring in the alkaline cell regions under illumination is associated with the acidic shift of cytoplasmic pH. Divergent amplitudes of ionic currents in different cell parts can be partially determined by the presence of numerous plasmalemmal invaginations, charasomes specifically localized in the acid zones, as well as by sharp local changes in external pH in acid zones during the perforation of cell wall with a measuring microelectrode.

中文翻译：

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质膜离子电流对Chara叶绿体中叶绿素荧光和激发猝灭的影响

摘要—

查拉藻藻类的发光巨细胞表现出膜兴奋性以及光合作用和跨膜H ⁺的空间格局通量。在这些条件下激发质膜导致外部碱性区和酸性区的瞬时降解，并抑制碱性区的光合作用。在图案化的节点间产生动作电位，然后是细胞超极化，该超极化在1分钟内达到峰值，并持续长达15分钟。为了排除静息电位漂移对叶绿体对质膜激发的响应的影响，在这项工作中应用了电压钳模式，并监测了短去极化脉冲引起的叶绿素荧光变化。发现在电压钳制条件下膜电位的去极化位移会引起大幅度降低\（F _ {{\ text {m}}} ^ {{{{}}} \）叶绿素荧光和光合作用，前提是向内Ca触发了²⁺和Cl ^–电流，并且在施加电刺激之前，稳态的内向H ⁺通量（或OH ^–外流）持续存在。发现在光和暗下在碱性和酸性细胞区域中测得的去极化诱导的离子电流明显不同。结果与以下观点一致：大量的内向H ⁺光照下碱性细胞区域中发生的血流与细胞质pH的酸性变化有关。不同细胞部分中离子电流的不同幅度可以部分由大量血浆缺陷的存在，特异定位在酸性区的charasomes的存在，以及通过在细胞壁上穿孔时酸性区中外部pH的急剧局部变化来确定。测量微电极。