Abstract
Fixation with a mixture of tannic acid and paraformaldehyde–glutaraldehyde resulted in an increased electron density of the membrane structure of tubular bodies that were associated with mycoplasma organisms (MLO) in Vinca rosea plants infected with the Alberta isolate of the aster yellows agent. The tubular bodies, 25.5 ± 4.3 nm in diameter, were bounded with membranes in contrast with the hollow cylinders of 12.3 ± 3.0 nm in conventional fixation. In the study of physical relationships, the tubular bodies were often connected with MLO by a common unit membrane. Some subtubules were formed from a main tubular body.