Laboratory of Chemical Biodynamics and Department of Chemistry, University of California, Berkeley, California 94720.
Plant Physiol. 1982 Jan;69(1):77-82. doi: 10.1104/pp.69.1.77.
Ethylenediaminetetraacetic acid (EDTA) enhanced the exudation of (14)C-labeled assimilates from excised leaflets and whole plant specimens of Fraxinus uhdei Wenz. A 2 millimolar EDTA concentration was found to be most effective in promoting exudation from excised leaflets, while 10 millimolar EDTA was most effective in whole plants experiments. Exudation rate reached a maximum after 24 hours in both experiments. The continuous presence of EDTA throughout the treatment period was required for maximum exudation from excised leaflets. Stachyose, raffinose, verbascose, and sucrose were the principal compounds found to occur in exudate samples. These compounds are typically transported in sieve elements of various Fraxinus species suggesting the exudate was of phloem origin. Electron microscope studies of petiolule sieve plate pores from excised leaflets showed substantially less callose appearing after treatment with EDTA than after H(2)O treatment. It is suggested that EDTA enhances phloem exudation by inhibiting or reducing callose formation in sieve plate pores. The exudation enhancement technique described for whole plant specimens is suggested as a useful means of collecting phloem sap and studying translocation in woody plants.
乙二胺四乙酸（EDTA）促进了白蜡树离体小叶和整株植物标本中（14）C 标记同化产物的渗出。发现 2 毫摩尔 EDTA 浓度最有效地促进离体小叶的渗出，而 10 毫摩尔 EDTA 最有效地促进整株植物实验的渗出。在这两种实验中，渗出率在 24 小时后达到最大值。在整个处理过程中持续存在 EDTA 是从离体小叶中获得最大渗出的必要条件。在渗出物样品中发现的主要化合物是棉子糖、棉子糖、毛蕊花糖和蔗糖。这些化合物通常在各种白蜡树属植物的筛管中运输，表明渗出物来自韧皮部。对离体小叶叶柄筛板孔的电子显微镜研究表明，在用 EDTA 处理后，出现的胼胝质明显少于用 H2O 处理后。因此，EDTA 通过抑制或减少筛板孔中的胼胝质形成来增强韧皮部渗出。描述的用于整株植物标本的渗出增强技术被建议作为收集韧皮部汁液和研究木质植物转运的有用方法。
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