Faculty of Natural Sciences, Institute for Plant Nutrition, Leibniz University Hannover, Herrenhäuserstr. 2, 30419 Hannover, Germany.
Physiol Plant. 2010 Jun 1;139(2):181-91. doi: 10.1111/j.1399-3054.2010.01355.x. Epub 2010 Jan 19.
The detoxification of aluminum (Al) in root tips of the Al accumulator buckwheat by exudation of oxalate leading to reduced Al uptake (Al resistance) is difficult to reconcile with the Al accumulation (Al tolerance). The objective of this study was to analyze resistance and tolerance mechanisms at the same time evaluating particularly possible stratification of Al uptake, Al transport and oxalate exudation along the root apex. The use of a minirhizotron made it possible to differentiate between spatial responses to Al along the root apex with regard to Al uptake and organic acid anion exudation, but also to measure at the same time Al and organic acid transport in the xylem. Al accumulates particularly in the 3-mm root apex. The study showed that Al taken up by the 10-mm root apex is rapidly transferred to the xylem which differentiates in the 10 to 15-mm root zone as revealed by a microscopic study. Al induces the release of oxalate from the root apex but particularly from the subapical 6-20 mm root zone even when Al was applied only to the 5-mm root apex suggesting a basipetal signal transduction. Citrate proved to be the most likely ligand for Al in the xylem because Al and citrate transport rates were positively correlated. In conclusion, the data presented show that the Al-induced release of oxalate, and Al uptake as well as Al accumulation are spatially not separated in the root apex.
根尖端的草酸分泌将铝（Al）解毒，导致铝吸收减少（铝抗性），这与铝积累（铝耐受性）难以协调。本研究的目的是同时分析抗性和耐受性机制，特别评估沿根根尖吸收、铝运输和草酸分泌的可能分层。使用迷你根管可以区分沿根根尖的 Al 吸收和有机酸阴离子分泌的空间响应，同时也可以测量木质部中的 Al 和有机酸运输。Al 特别积累在 3mm 的根尖。研究表明，10mm 根尖吸收的 Al 迅速转移到木质部，这在 10 到 15mm 的根区通过显微镜研究得到了区分。Al 诱导根尖释放草酸，但特别是从亚根尖 6-20mm 的根区释放，即使 Al 仅施加在 5mm 的根尖也暗示了向根基的信号转导。柠檬酸被证明是木质部中 Al 的最可能配体，因为 Al 和柠檬酸运输速率呈正相关。总之，所提出的数据表明，在根尖端，铝诱导的草酸释放、铝吸收以及铝积累在空间上没有分离。
