School of Biological Sciences, University of Sussex, Brighton, UK.
Planta. 1971 Dec;98(4):285-93. doi: 10.1007/BF00380229.
The water-extractable and ion-exchangeable fractions of the free space of maize roots for sodium ions has been determined. The free space of whole roots, excised roots and isolated stelar and cortical tissues, has been compared and the results examined for any evidence of a barrier between the cortex and the stele. Similarly the free space of whole roots and excised roots, from which the epidermal and outer cortical cells have been removed by shaving, has been compared and the results examined for any evidence of an epidermal barrier.Whole roots gave a free space value some 20% lower than excised roots. It was calculated that this difference could be accounted for if the cortical tissues only were considered in estimating the whole root value, that is if the stele was considered as participating in the excised root but not in the whole root. Samples in which isolated cortical and stelar material were measured together, or separately and the value calculated, gave similar values to those obtained for excised roots. These results are interpreted as evidence that a barrier to free diffusion exists between the cortical and the stelar tissues at or near the endodermis. Shaving both whole and excised roots increased the free space by about 35%. However, as this value was similar for both, it was concluded that the increase was due to the contribution of damaged cortical cells and does not indicate that the epidermis is an effective barrier to the diffusive entry of sodium ions into the root.
已测定玉米根自由空间中钠离子的可提取水相和可交换离子相分数。比较了完整根、离体根以及分离的中柱和皮层组织的自由空间，并检查结果中是否存在皮层和中柱之间的屏障的证据。同样，还比较了完整根和离体根的自由空间，这些离体根通过刮削去除了表皮和外皮层细胞，并检查结果中是否存在表皮屏障的证据。完整根的自由空间值比离体根低约 20%。据计算，如果仅考虑皮层组织来估计整个根的值，也就是说，如果将中柱视为参与离体根但不参与整个根，则可以解释这种差异。将分离的皮层和中柱材料一起测量或分开测量并计算值的样品，得到的值与离体根的结果相似。这些结果表明，在根内皮层附近，皮层和中柱组织之间存在自由扩散的屏障。刮削完整根和离体根都会使自由空间增加约 35%。然而，由于两者的值相似，因此可以得出结论，增加是由于受损的皮层细胞的贡献，而不是表皮对钠离子扩散进入根内具有有效的屏障。
