Plant Bioelectrics Group, Institute of Pulsed Power and Microwave Technology and Institute of Botany 1, Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen, Germany.
Plant Cell Environ. 2011 May;34(5):859-69. doi: 10.1111/j.1365-3040.2011.02291.x.
Early events in NaCl-induced root ion and water transport were investigated in maize (Zea mays L) roots using a range of microelectrode and imaging techniques. Addition of 100 mm NaCl to the bath resulted in an exponential drop in root xylem pressure, rapid depolarization of trans-root potential and a transient drop in xylem K(+) activity (A(K+) ) within ∼1 min after stress onset. At this time, no detectable amounts of Na(+) were released into the xylem vessels. The observed drop in A(K+) was unexpected, given the fact that application of the physiologically relevant concentrations of Na(+) to isolated stele has caused rapid plasma membrane depolarization and a subsequent K(+) efflux from the stelar tissues. This controversy was explained by the difference in kinetics of NaCl-induced depolarization between cortical and stelar cells. As root cortical cells are first to be depolarized and lose K(+) to the environment, this is associated with some K(+) shift from the stelar symplast to the cortex, resulting in K(+) being transiently removed from the xylem. Once Na(+) is loaded into the xylem (between 1 and 5 min of root exposure to NaCl), stelar cells become more depolarized, and a gradual recovery in A(K+) occurs.
采用一系列微电极和成像技术研究了盐诱导玉米（Zea mays L）根中离子和水转运的早期事件。将 100 mM NaCl 添加到浴液中会导致根木质部压力呈指数下降，跨根电势迅速去极化，以及在胁迫开始后约 1 分钟内木质部 K+活性（A(K+)）短暂下降。此时，木质部导管中没有检测到可检测量的 Na+释放。考虑到生理相关浓度的 Na+施加到分离的中柱时会导致质膜迅速去极化，随后从中柱组织中排出 K+，因此观察到的 A(K+)下降是出乎意料的。这种争议可以通过盐诱导去极化在皮层和中柱细胞之间的动力学差异来解释。由于根皮层细胞首先去极化并将 K+释放到环境中，因此与从中柱共质体向皮层的一些 K+转移相关，导致 K+暂时从木质部中去除。一旦 Na+被加载到木质部中（根暴露于 NaCl 1 至 5 分钟之间），中柱细胞变得更加去极化，A(K+)逐渐恢复。
