Visualizing plant-pathogen interactions involving phenolics

2 Visualizing plant-pathogen interactions involving phenolics with histochemical stains 

As most phenols are found as esters or glycosides, knowledge of their location in a cell or tissue is essential. It is typical that such phenols are sequestered or stored in the cell vacuole. This is important since all phenols are weak acids (see Chapter 2) and as such they are relatively toxic even to 

Inoculation of maize roots with the non-pathogen Phytophthora cinnamomi also resulted in production of papillae (Hindi and Clarke, 1980). Callose was reported as the major component of the papillae, and carbohydrates but not proteins were identified. Lignin did not appear to be 

Different histochemical tests have been used for peroxidase identification. Benzidine (4.33) has been used as a staining reagent, as well as guaiacol (4.34) and pyrogallol (4.35). However, until the 1970s, no reliable methods were known that allowed a sharp discrimination between oxidase and peroxidase activities (Maehly and Chance, 1954). Harkin and Obst (1973) reported the syringaldazine (4.36) histochemical test for peroxidase. This test permitted the proof of exclusive peroxidase participation in the lignification process. 

Cytochemical identification of peroxidase was conducted in infected wound margins in the cell walls and degenerating cytoplasm of wheat leaves with 3,3 -diaminobenzidine (Thorpe and Hall, 1984). The same substrate 

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