Distribution and organization of articulated laticifers in Calystegia silvatica (Convolvulaceae)

The distribution and organization of mostly mature laticifers in shoots and roots of Calystegia silvatica (Kit.) Griesb. are described. Some of the effects caused by specimen preparation for light and electron microscopy, using chemical fixation and physical freezing methods, are also noted. The laticifers form long straight unbranched articulated tubes throughout the pith, cortex, and phloem. The end walls of the cells are usually perforated by a circular aperture occupying part of the wall. A distinctive layer of suberin-like material impregnates the cell wall. A milky-white latex of numerous spherical particles fills the large central vacuole, restricting the cytoplasm to a thin layer against the cell wall. This latex is preserved within the laticifer when living tissues are frozen, fractured, and freeze-dried for scanning electron microscopy, but often the latex particles and cytoplasm are destroyed when tissues are chemically processed for thin sectioning and transmission electron microscopy. Attempts to improve retention and preservation of the latex by varying parameters of fixation and dehydration were largely unsuccessful. Cytochemical tests indicate the latex particles are mainly lipid in composition.