LAUSR

Abstract Cork cells from Quercus variabilis Blume were examined with transmission electron microscopy to detect the occurrence of plasmodesmata (PD). Ultrastructural analysis revealed the distribution, morphology and internal structure of PD in cork. PD were membrane-lined channels and there were numerous PD through the adjacent cork cells, which established symplastic communication pathway in the phellem tissue. Plasmodesmal distribution varied from uniformly distributed individual plasmodesma to random arrangements or discrete groups. The simple and complex morphology of PD were observed in neighboring cork cells. The desmotubule was in the centre of PD and an electron-opaque centre within the desmotubule was a proteinaceous central rod. The desmotubule of some PD exhibited conspicuous constriction in the suberized layer of the secondary wall of adjacent cells and expanded central zone in the compound middle lamella. Calotte deposition with higher electron density accumulated inside the cell at the aperture was found at the end of some PD channels.