Collings D A, White R G, Overall R L
School of Biological Sciences, Macleay Building A12, University of Sydney, New South Wales 2006, Australia.
Plant Physiol. 1992 Nov;100(3):1417-26. doi: 10.1104/pp.100.3.1417.
A vibrating probe was used to measure the changes in ionic currents around gravistimulated roots of Zea mays L. in an effort to determine whether these currents are involved in stimulus transduction from the root cap to the elongation zone. We did not observe a migration of the previously reported auxin-insensitive current efflux associated with gravity sensing (T. Björkman, A.C. Leopold [1987] Plant Physiol 84:841-846) back from the root cap. Instead, beginning 10 to 15 min after gravistimulation, an asymmetry in current developed simultaneously along the root around the meristem and apical regions of the elongation zone. This asymmetry comprised a proton efflux from the upper surface, which was superimposed on the symmetrical pattern around the vertical root. The gravity-induced proton efflux was inhibited by the application of the auxin transport inhibitor, 2,3,5-triiodobenzoic acid, whereas the calcium channel blocker, lanthanum, had little effect. Because the onset of the gravity-induced current asymmetry coincided both spatially and temporally with the onset of the differential growth response, we suggest that this current efflux may result from auxin-requiring acid-growth phenomena in the upper root tissue. The implications of this simultaneous onset of both proton efflux and elongation for theories about gravity stimulus transduction are discussed.
使用振动探针测量了重力刺激下玉米根周围离子电流的变化，以确定这些电流是否参与了从根冠到伸长区的刺激传导。我们没有观察到先前报道的与重力感应相关的生长素不敏感电流外流（T. 比约克曼、A.C. 利奥波德 [1987]《植物生理学》84:841 - 846）从根冠回流。相反，在重力刺激开始10到15分钟后，沿着根在伸长区的分生组织和顶端区域周围同时出现了电流不对称。这种不对称包括上表面的质子外流，它叠加在垂直根周围的对称模式上。重力诱导的质子外流受到生长素运输抑制剂2,3,5 - 三碘苯甲酸的抑制，而钙通道阻滞剂镧的影响很小。由于重力诱导的电流不对称的开始在空间和时间上都与差异生长反应的开始相吻合，我们认为这种电流外流可能是由于根上部组织中需要生长素的酸生长现象导致的。本文讨论了质子外流和伸长同时开始对重力刺激传导理论的意义。
