Jackson P C, Edwards D G
J Gen Physiol. 1966 Sep;50(1):225-41. doi: 10.1085/jgp.50.1.225.
Accumulation of Cl(-) by excised barley roots, as of K(+), approaches a maximum level at which the ion influx and efflux rates become equal. The rate of Cl(-) influx at this equilibrium is close to the initial rate while the efflux rate increases with time from zero to equality with influx. The Cl(-) fluxes are independent of simultaneous exchange flux of the cations, but depend on the nature and concentration of the salt solutions from which they originate. The Cl(-) content at equilibrium, however, is largely independent of the external concentrations. The approach to equilibrium reflects the presence of the cation. Cl(-) flux equilibrium is attained more rapidly in KCl than in CsCl or CaCl(2). This is presumably an effect of much slower distribution of Cs(+) and Ca(++) than of K(+) within the roots. Accumulated Cs(+) appears to form a barrier to ion movement primarily within the outermost cells, thereby reducing influx and ultimately efflux rates of both Cl(-) and cations. Slow internal mixing and considerable self-exchange of the incoming ions suggest internal transport over a series of steps which can become rate-limiting to the accumulation of ions in roots.
与钾离子一样，离体大麦根对氯离子的积累接近一个最大水平，此时离子的流入和流出速率相等。在这个平衡状态下，氯离子的流入速率接近初始速率，而流出速率则随时间从零增加到与流入速率相等。氯离子通量与阳离子的同时交换通量无关，但取决于它们所源自的盐溶液的性质和浓度。然而，平衡时的氯离子含量在很大程度上与外部浓度无关。达到平衡的过程反映了阳离子的存在。在氯化钾中比在氯化铯或氯化钙中能更快地达到氯离子通量平衡。这可能是因为铯离子和钙离子在根内的分布比钾离子慢得多。积累的铯离子似乎主要在最外层细胞内形成离子移动的屏障，从而降低了氯离子和阳离子的流入速率以及最终的流出速率。缓慢的内部混合以及进入离子的大量自我交换表明内部运输是通过一系列步骤进行的，这些步骤可能会成为限制离子在根中积累的速率因素。
