Fusiform cells in the cambium of Kalopanax pictus are exclusively mononucleate.

While it is generally accepted that most plant cells are mononucleate, it has been argued with some vehemence that fusiform cambial cells can be multinucleate. The controversy has not been resolved since to date, studies by conventional microscopy and transmission electron microscopy have failed to confirm unambiguously whether cambial cells are mononucleate or multinucleate. In this study, semi-thin sections of epoxy-embedded specimens and thick slices of cambial tissues from the hardwood Kalopanax pictus were analysed by confocal laser scanning microscopy. Tangential sections of cambium, regardless of the thickness of the section, are likely to contain portions of cells in several adjacent layers of cells and, at the lower resolution of conventional microscopy, several adjacent cells can appear to be a single cell with more than one nucleus. The higher resolution in the third dimension of confocal microscopy allowed clearly adjacent layers of cells in the cambium to be distinguished and the number of nuclei per cell to be determined. In this tree, the cambial cells were mononucleate in all cases.