Preventing False Negatives for Histochemical Detection of Phenolics and Lignins in PEG-Embedded Plant Tissues

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 p...

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Bibliographic Details
Published in:The journal of histochemistry and cytochemistry 2017-02, Vol.65 (2), p.105-116
Main Authors: Ferreira, Bruno G., Falcioni, Renan, Guedes, Lubia M., Avritzer, Sofia C., Antunes, Werner C., Souza, Luiz A., Isaias, Rosy M.S.
Format: Article
Language:English
Subjects:
Anacardiaceae - chemistry
Anacardiaceae - ultrastructure
Fixatives - chemistry
Flavonols - analysis
Lignin - analysis
Melastomataceae - chemistry
Melastomataceae - ultrastructure
Microscopy, Fluorescence - methods
Nicotiana - chemistry
Nicotiana - ultrastructure
Phenols - chemistry
Plants - chemistry
Plants - ultrastructure
Polyethylene Glycols - chemistry
Polyphenols - analysis
Staining and Labeling - methods
Tannins - analysis
Tissue Embedding - methods
Tissue Fixation - methods
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Summary: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.
ISSN:0022-1554
1551-5044
DOI:10.1369/0022155416677035