Appalachian Soil and Water Conservation Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beckley, West Virginia 25802-0867.
Plant Physiol. 1990 Aug;93(4):1620-5. doi: 10.1104/pp.93.4.1620.
Dissolved aluminum (III) in acidic soils or culture media is often rhizotoxic (inhibitory to root elongation). Alkaline solutions of Al are also sometimes rhizotoxic, and for that reason toxicity has been attributed to the aluminate ion, Al(OH)(4) (-). In the present study, seedlings of wheat (Triticum aestivum L. cv Tyler) and red clover (Trifolium pratense L. cv Kenland) were cultured in aerated aluminate solutions at pH 8.0 to 8.9. The bulk phases of these solutions were free of reactive polynuclear hydroxy-Al (including the extremely toxic species AlO(4)Al(12)OHH(2)O (12) [Al(13)]) according to the ferron (8-hydroxy-7-iodo-5-quinolinesulfonic acid) assay. At an aluminate concentration of 25 micromolar (23 micromolar activity) and a pH of 8, root elongation was less than 40% of Al-free controls, but at pH 8.9 elongation was 100% of controls. The hypothesis is offered that aluminate is nontoxic and that the inhibition at lower pH values is attributable to Al(13) postulated to have formed in the acidic free space of the roots where the ratio /{Al(3+)/}//{H(+)/}(3) may rise above 10(10). At this value hydroxy-Al in over-saturated, alkaline solutions begins to undergo rapid conversion to polynuclear species.
溶解在酸性土壤或培养基中的三价铝通常对根伸长具有毒性（抑制根伸长）。碱性的铝溶液有时也具有毒性，因此毒性归因于铝酸根离子，Al(OH)(4) (-)。在本研究中，小麦（Triticum aestivum L. cv Tyler）和红三叶草（Trifolium pratense L. cv Kenland）的幼苗在 pH 值为 8.0 至 8.9 的充氧铝酸盐溶液中培养。根据 ferron（8-羟基-7-碘-5-喹啉磺酸）测定法，这些溶液的主体相不含反应性多核羟基-Al（包括极其有毒的物种 AlO(4)Al(12)OHH(2)O (12) [Al(13)])。在 25 微摩尔（23 微摩尔活度）的铝酸盐浓度和 pH 值为 8 的条件下，根伸长小于无铝对照的 40%，但在 pH 值为 8.9 时，伸长率为对照的 100%。提出的假设是，铝酸盐是无毒的，较低 pH 值下的抑制作用归因于在根部的酸性自由空间中假定形成的 Al(13)，其中/ {Al(3+)/} / {H(+)/} (3)的值可能超过 10(10)。在这个值下，过饱和碱性溶液中的羟基-Al 开始快速转化为多核物种。
