CHLOROPLAST MICROTUBULES IN OEDOGONIUM CAPILLIFORME (CHLOROPHYTA) 1

Microtubular elements in the chloroplasts (chl‐MTs) of Oedogonium capilliforme Wittrock were examined by conventional electron microscopy and immunoelectron microscopy. Chl‐MTs were frequently seen in the terminal, convex, and concave peripheral regions of the chloroplasts. Each bundle of chl‐MTs was composed of 2–25 tubular elements. Some chl‐MTs were located in the stroma. Chl‐MTs frequently bridged two areas of the envelope membrane near the apex of convex regions of chloroplasts. Some chl‐MTs were closely associated with the envelope membrane via apparent anchors along their length. The distribution patterns of chl‐MTs and their appearance suggest that chl‐MTs are involved in the maintenance of the outer shape of chloroplasts. However, immunoelectron microscopy with an antibody against α‐tubulin indicated that the chl‐MTs are not composed of tubulin.