Clarkson D T, Sanderson J
Agricultural Research Council, Letcombe Laboratory, Wantage, OX12 9JT, Great Britain.
Plant Physiol. 1978 May;61(5):731-6. doi: 10.1104/pp.61.5.731.
Absorption and translocation of labeled Fe were measured at various locations along the length of intact seminal axes and lateral roots of iron-sufficient (+Fe) and iron-stressed (-Fe) barley (Hordeum vulgare) plants. In seminal axes of +Fe plants, rates of translocation were very much higher in a zone 1 to 4 cm from the root tip than elsewhere in the root. Lateral roots of high rates of translocation were also restricted to a narrow band of maturing or recently matured cells. In -Fe plants the patterns of uptake and translocation were essentially the same as in +Fe plants but the rates were 7- to 10-fold higher. The amount of labeled Fe bound to the root itself was not increased by Fe stress and its distribution along the root seemed inversely related to the ability to translocate Fe.Microautoradiographic studies showed that most of the iron bound to roots was held in an extracellular peripheral band in which iron seemed to be precipitated. This process may be assisted by microbial colonies but did not depend on them since it was seen, although to a lesser extent, in sterile roots. In zones from which iron was translocated there was evidence that internal root tissues became labeled readily, but as translocation declined with distance from the root tip, radial penetration of Fe appeared to become progressively less. The results are discussed in relation to possible changes in the pH or redox potential of the surface of the root.
在铁充足（+Fe）和铁胁迫（-Fe）的大麦（Hordeum vulgare）植株完整的胚轴和侧根的不同部位，测量了标记铁的吸收和转运情况。在+Fe植株的胚轴中，根尖1至4厘米区域的转运速率比根的其他部位高得多。侧根中转运速率高的部位也局限于成熟或刚成熟细胞的窄带区域。在 -Fe植株中，吸收和转运模式与+Fe植株基本相同，但速率高出7至10倍。铁胁迫并未增加根自身结合的标记铁的量，且其在根上的分布似乎与铁的转运能力呈负相关。显微放射自显影研究表明，与根结合的大部分铁存在于细胞外周带，铁似乎在其中沉淀。这个过程可能得到微生物菌落的辅助，但并不依赖于它们，因为在无菌根中也能观察到这一现象，尽管程度较轻。在铁被转运的区域，有证据表明根内部组织很容易被标记，但随着离根尖距离增加转运下降，铁的径向渗透似乎逐渐减少。结合根表面pH值或氧化还原电位可能发生的变化对结果进行了讨论。
