Craig L. Nessler

Cell Wall Perforation in Laticifers of Papaver somniferum L.

Cell wall perforation in the articulated anastomosing laticifers of the opium poppy, Papaver somniferum L., was examined by electron microscopy. Perforation resulted from a gradual thinning of the walls on both sides of the middle lamella. Thinning occurred uniformly over transverse walls during articulation and at localized sites along lateral walls during anastomosis. Electron-dense globular deposits were seen at perforation sites; their function in the perforation process was not apparent. The progressive and simultaneous thinning of the cell wall on either side of the middle lamella at the site of a developing perforation suggests that wall-degrading enzymes (cellulases), rather than pressure, may be involved in the wall-perforation process.

Ultrastructural Observations of Extranuclear Temperature-Sensitive Lethality in Nicotiana tabacum L.

Extranuclear temperature-sensitive lethality in Nicotiana tabacum L. was investigated at the ultrastructural level. Chloroplasts of temperature-sensitive and control plants were morphologically similar in plants grown at nonlethal temperatures (26 C day/20 C night); both possessed typical lamellar structure, starch grains, and plastoglobuli. At lowered temperatures (13 C day/8 C night), chloroplasts in temperature-sensitive plants gradually degenerated as evidenced by the disappearance of starch, increase in plastoglobuli, and the formation of numerous vesicles from the dilation of thylakoids. Chloroplasts in control plants continued to accumulate starch in several large grains, occupying most of the plastid volume by the end of the investigation. Mitochondria in both temperature-sensitive and control plants were morphologically unaltered by exposure to lowered temperatures. Ultrastructural evidence suggests that the site of inheritance of extranuclear temperature-sensitive lethality in the mutant is in the chloroplast.

Laticifers in Stamens of Papaver somniferum L.

SummaryArticulated anastomosing laticifers were identified at both light and electron microscopic levels in the stamens of Papaver somniferum L. They were observed associated with the phloem forming a continuous system from the filament into the anther of the stamen. Laticifers, which were comparable in structure to laticifers found elsewhere in the plant, possessed numerous vesicles of different sizes within the protoplast.