Ferreira Bruno G, Falcioni Renan, Guedes Lubia M, Avritzer Sofia C, Antunes Werner C, Souza Luiz A, Isaias Rosy M S
Departamento de Botânica/Pós-Graduação em Biologia Vegetal, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil (BGF, SCA, RMSI).
Departamento de Biologia/Pós-Graduação em Agronomia/Biologia Comparada, Universidade Estadual de Maringá, Maringá, Brazil (RF, WCA, LAS).
J Histochem Cytochem. 2017 Feb;65(2):105-116. doi: 10.1369/0022155416677035. Epub 2016 Nov 12.
Polyethylene glycol (PEG) is a low-cost and advantageous embedding medium, which maintains the majority of cell contents unaltered during the embedding process. Some hard or complex plant materials are better embedded in PEG than in other usual embedding media. However, the histochemical tests for phenolics and lignins in PEG-embedded plant tissues commonly result in false negatives. We hypothesize that these false negatives should be prevented by the use of distinct fixatives, which should avoid the bonds between PEG and phenols. Novel protocols for phenolics and flavanols detection are efficiently tested, with fixation of the samples in ferrous sulfate and formalin or in caffeine and sodium benzoate, respectively. The differentiation of lignin types is possible in safranin-stained sections observed under fluorescence. The Maule's test faultlessly distinguishes syringyl-rich from guaiacyl- and hydroxyphenyl-rich lignins in PEG-embedded material under light microscopy. Current hypothesis is corroborated, that is, the adequate fixation solves the false-negative results, and the new proposed protocols fill up some gaps on the detection of phenolics and lignins.
聚乙二醇（PEG）是一种低成本且具有优势的包埋介质，它能在包埋过程中使大部分细胞内容物保持不变。一些坚硬或复杂的植物材料在PEG中比在其他常用包埋介质中更易于包埋。然而，对PEG包埋的植物组织中酚类和木质素进行组织化学检测时通常会出现假阴性结果。我们推测，使用不同的固定剂应可避免PEG与酚类之间的结合，从而防止这些假阴性结果的出现。分别用硫酸亚铁和福尔马林或咖啡因和苯甲酸钠固定样品，对酚类和黄烷醇检测的新方案进行了有效测试。在荧光下观察番红染色切片时，可以区分木质素类型。在光学显微镜下，Maule试验能完美地区分PEG包埋材料中富含紫丁香基的木质素与富含愈创木基和对羟基苯基的木质素。当前的推测得到了证实，即适当的固定可解决假阴性结果，并且新提出的方案填补了酚类和木质素检测方面的一些空白。
