Plasmodesmata are complex channels within the plant cell wall, which create
plasma membrane and symplastic continuity between neighbouring cells. To d
etect plasmodesmata in cell wall preparations from Nicotiana de elandii, we
have used 3,3'-dihexyloxacarbocyanine iodide (DiOC(6)), a cationic amphiph
ilic fluorescent probe, widely employed for general studies of membrane str
ucture and dynamics. Punctate fluorescent staining was readily seen in pit
fields, small depressions within the cell wall known to be rich in plasmode
smata. Scanning electron microscopy was used to demonstrate that the puncta
te staining corresponded to plasmodesmata. Treatment of cell wail fragments
with chloroform-methanol to remove lipids did not alter the staining of pl
asmodesmata. In contrast, pronase E-sodium dodecyl sulfate treatment comple
tely abolished staining, indicating that the DiOC(6) labelling of plasmodes
mata may be protein rather than lipid specific. Although not membrane media
ted, DiOC(6) staining of plasmodesmata is a simple, rapid, and specific too
l for the detection of plasmodesmata in isolated cell walls and will prove
useful for studies of plasmodesmal location, structure, and composition.