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Cytoplasmic Changes During and After Infection of Soybean Root Nodule Cells with Rhizobia. J. C. Tu, Biological Sciences Electron Microscope Laboratory, University of Alberta, Edmonton, Alberta, Canada T6G 2E1; Phytopathology 66:1065-1071. Accepted for publication 8 March 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-1065.

Root cortical cells adjacent to or invaded by infection threads underwent cytoplasmic changes. These changes included an increase in number of ribosomes, and the extension of endoplasmic reticulum. The changes indicate increased cellular synthetic activities. These cellular changes continued throughout the life of the cells. Upon release of the rhizobia from the infection thread into the cytoplasm, the number of dictyosomes increased. These dictyosomes were arranged in a long chain between the rhizobial bacteroids and the interior nucleus of the cell. Similarly, vesicles of dictyosome origin greatly increased in number, and often fused into a large vesicular body that was deposited around the rhizobia. The content of these vesicles and vesicular bodies had staining properties similar to that of the cell plate or middle lamella, as demonstrated by a differential staining technique. Increased dictyosome activity receded after the rhizobial bacteroids were released into the cells. Therefore, I suspect that the transitory increase of dictyosome activity may be attributed to stimulated production of cell wall materials induced by the invasion of infection threads and the release of rhizobial bacteria.