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Cytology and Histology

Localized Cell Wall Appositions: Incompatibility Response of Tobacco Leaf Cells to Pseudomonas pisi. D. J. Politis, Research Microbiologist, Department of Plant Pathology, University of Missouri-Columbia, Columbia, MO 65201; R. N. Goodman, professor, Department of Plant Pathology, University of Missouri-Columbia, Columbia, MO 65201. Phytopathology 68:309-316. Accepted for publication 15 August 1977. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-309.

Two hr after tobacco leaf tissue was inoculated with Pseudomonas pisi (nonpathogenic to tobacco), the bacteria were localized in close proximity to plant cell walls. The plasmalemma in cells opposite the bacteria is convoluted and separates from the inner wall layers. Three to 4 hr later, loose microfibrillar material accumulated in the area between the plasmalemma and the inner wall layers directly opposite the localized bacteria. This accumulation was called a cell wall apposition. Six hr later the cell wall appositions were well organized massive structures that invaginated the plasmalemma. They appeared to be striated, an effect which reflected variations in packing density of the component microfibrils; membrane-bound vesicles frequently were found embedded within the layers of the electron-dense microfibrils. The vesicles originated from the convoluted plasmalemma opposite the attached bacteria and appeared to carry and deposit the microfibrillar materials that form the cell wall apposition. During the first 6 hr the general membrane damage that usually is associated with the hypersensitive reaction in cells was not noticeable. These observations suggested that pronounced cell wall appositions consist of newly synthesized cell wall material that is formed as a part of a complex series of reactions that lead to tobacco leaf cell death caused by the incompatible bacteria.