F-actin in conifer roots.

The distribution of F-actin in the complex tissues of a higher plant organ has been visualized by fluorescence labeling the roots of the conifers Chamaecyparis obtusa and Pseudotsuga menziesii with F-actin-specific fluorescent dye-conjugated phallicidin. F-actin is present in the parenchymatous cells of the vascular tissue. Some vascular parenchyma cells possess larger numbers of F-actin-containing structures (microfilament bundles) than are known to exist in any other higher plant cell. Tissue type appears to be an important determinant of the presence or absence of F-actin in a cell. For example, in contrast to vascular cells, cortical cells show no indication of fluorescence labeling of F-actin after incubation with fluorescent phallicidin. Cytoplasmic streaming is seen only in vascular cells and in a pattern that reflects the intracellular distribution of F-actin.