title: Preventing False Negatives for Histochemical Detection of Phenolics and Lignins in PEG-Embedded Plant Tissues.
abstract: 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.
authors.affiliation: Departamento de Botânica/Pós-Graduação em Biologia Vegetal, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil (BGF, SCA, RMSI).
authors.forename: Bruno G
authors.initials: BG
authors.lastname: Ferreira
authors.affiliation: Departamento de Biologia/Pós-Graduação em Agronomia/Biologia Comparada, Universidade Estadual de Maringá, Maringá, Brazil (RF, WCA, LAS).
authors.forename: Renan
authors.initials: R
authors.lastname: Falcioni
authors.affiliation: Postgrados en Ciências Biológicas - área Botánica, Universidad de Concepción, Concepción, Chile (LMG).
authors.forename: Lubia M
authors.initials: LM
authors.lastname: Guedes
authors.affiliation: Departamento de Botânica/Pós-Graduação em Biologia Vegetal, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil (BGF, SCA, RMSI).
authors.forename: Sofia C
authors.initials: SC
authors.lastname: Avritzer
authors.affiliation: Departamento de Biologia/Pós-Graduação em Agronomia/Biologia Comparada, Universidade Estadual de Maringá, Maringá, Brazil (RF, WCA, LAS).
authors.forename: Werner C
authors.initials: WC
authors.lastname: Antunes
authors.affiliation: Departamento de Biologia/Pós-Graduação em Agronomia/Biologia Comparada, Universidade Estadual de Maringá, Maringá, Brazil (RF, WCA, LAS).
authors.forename: Luiz A
authors.initials: LA
authors.lastname: Souza
authors.affiliation: Departamento de Botânica/Pós-Graduação em Biologia Vegetal, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil (BGF, SCA, RMSI).
authors.forename: Rosy M S
authors.initials: RM
authors.lastname: Isaias
mesh_terms: D027926:Anacardiaceae / Q000737:chemistry / Q000648:ultrastructure; D005404:Fixatives / Q000737:chemistry; D044948:Flavonols / Q000032:analysis; D008031:Lignin / Q000032:analysis*; D035322:Melastomataceae / Q000737:chemistry / Q000648:ultrastructure; D008856:Microscopy, Fluorescence / Q000379:methods; D010636:Phenols / Q000737:chemistry*; D010944:Plants / Q000737:chemistry* / Q000648:ultrastructure*; D011092:Polyethylene Glycols / Q000737:chemistry*; D059808:Polyphenols / Q000032:analysis; D013194:Staining and Labeling / Q000379:methods; D013634:Tannins / Q000032:analysis; D016610:Tissue Embedding / Q000379:methods*; D016707:Tissue Fixation / Q000379:methods; D014026:Nicotiana / Q000737:chemistry / Q000648:ultrastructure
chemical_list: D005404:Fixatives; D044948:Flavonols; D010636:Phenols; D059808:Polyphenols; D013634:Tannins; D011092:Polyethylene Glycols; D008031:Lignin
keywords: epifluorescence; flavanols; lignins; plant anatomy; plant histochemistry; polyphenols; tannins