ABSTRACT
The presence of bacterial pathogens in plant host tissues and the change they cause in these plant tissues are studied by histopathology of infected plant material. The location of the bacterial pathogen as intercellular or intracellular or in water conducting tissues can be revealed with microtome sectioning and staining of the plant cellular material. The most desirable killing and fixing solutions are formalin–acetic acid–alcohol (FAA) and the FAA saturated with mercuric chloride. The advantage of the latter is that it helps to bind the bacterial cells together and thus keeps the bacterial mass intact without leaching or dispersal during sectioning and staining. The phloroglucinol test for lignin also holds good for wound gums and gives a red color while is present mainly in cell walls of vascular tissue and sclerenchyma. The wound gums accumulate in the intercellular spaces and lumina of parenchyma and within the vessels adjacent to the bacterial mass.
