School of Biological Sciences, University of Sussex, BN1 9QG, Brighton, UK.
Planta. 1973 Dec;112(4):293-9. doi: 10.1007/BF00390302.
The accumulation of (86)Rb labelled potassium by isolated stelar and cortical tissues from 7-day-old roots of Zea mays has been compared with the levels accumulated by these tissues in the intact root. Cortical tissues have similar uptake eapacities in these two conditions whereas stelar tissues only exhibit an uptake capacity in the intact root system. The uncoupler carbonylcyanide m-chlorophenylhydrazone caused a considerable decrease in the uptake of potassium by these tissues. In the intact root system it prevented ions from the bathing medium reaching the stelar tissues. The efflux pattern from preloaded isolated stelar and cortical tissues was considerably altered by the inhibitor, a promotion of the efflux occurring in both of these tissues.It is concluded that stelar tissues only accumulated ions when these are supplied through the root symplasm and that the stelar plasmalemma has only a limited uptake capacity per se. Stelar uptake is thus a reflection of vacuolar accumulation across the tonoplast. There is no evidence in the present study of a carrier-mediated active secretion of ions across the stelar plasmalemma. The fact that the efflux was promoted rather than depressed by the uncoupler supports the postulate that a passive leakage is the final stage in the transport of ions across the plant root.
将 7 天龄玉米根中分离的茎和皮层组织积累的（86）Rb 标记钾与完整根系中积累的水平进行了比较。在这两种情况下，皮层组织具有相似的摄取能力，而茎组织仅在完整根系中表现出摄取能力。解偶联剂羰基氰化物 m-氯代苯腙导致这些组织对钾的摄取大量减少。在完整的根系系统中，它阻止了来自浴液的离子到达茎组织。抑制剂从预加载的分离茎和皮层组织中流出的模式发生了很大的变化，促进了这两种组织中钾的流出。因此，可以得出结论，只有当离子通过根共质体供应时，茎组织才会积累离子，而茎质膜本身的摄取能力有限。因此，茎的摄取反映了液泡穿过质膜的积累。本研究没有证据表明离子通过茎质膜的载体介导的主动分泌。解偶联剂促进而不是抑制流出的事实支持这样的假设，即被动渗漏是离子跨植物根运输的最后阶段。
