Microbodies and an anomalous "microcylinder" in the ultrastructure of plants with Crassulacean acid metabolism.

An ultrastructural study was made of the leaf tissues of four species of plants in three genera with Crassulacean acid metabolism ("CAM" plants): Kalanchoë daigremontiana Hamet et Perrier, K. verticillata Elliot, Sedum rubrotinctum clausen and Crassula tetragona L. Microbodies similar in appearance, with fibrillar or granular nucleoids but no crystalline deposits, were present in the mesophyll of all four species. The microbodies resembled in size and abundance those of C3 plants more closely than those of C4 plants, both under long-day and short-day conditions. The reaction for catalase activity employing 3,3'-diaminobenzidine produced a heavy deposit in the microbodies; the reaction was blocked by the catalase inhibitor, aminotriazole.Some of the plants of the two species of Kalanchoë studied contain in the epidermal and mesophyll cells of the leaves and plantlets an organelle-like structure consisting of a hollow cylinder, 90-160 nm in diameter and up to 2 μm or more in length, around which 18-20 or more minute tubules are wound in a steep helix. The tubules are only ca. 9 nm in diameter, hence are much smaller than conventional microtubules. The cylinder and surrounding tubules, herein tentatively assigned the term "microcylinder" for convenience, may represent a product of viral infection, or may be an organelle that appears at certain stages of growth or under particular environmental conditions. In any case it may prove to be of considerable importance for investigators of CAM plant physiology.