Continuity of the Chloroplast Membrane Systems in Zea mays L.

Ultrastructural studies of the chloroplasts of the normal, yellow-green, and pale green phenotypes of Zea mays L. indicate that the internal membrane system is continuous with the plastid envelop. The intramembraneous spaces, loculi, and fret channels are also continuous with inner component of the plastid envelop. High energy compounds or other photosynthates, formed in the grana or frets are thus separated from both stroma and cytoplasm by a single membrane, either the fret membrane or the outer component of the plastid envelop. Since this type of plastid ultrastructure is apparently found only in plants exhibiting the Hatch and Slack pathways of photosynthesis there may be a relation between plastid ultrastructure and the pathways of photosynthetic carbon fixation.