Ultrastructural studies of isolatedZea mays L. Chloroplasts

Summary The ultrastructure of isolated mesophyll chloroplasts ofZea mays L. was studied using the shadow casting technique. Grana and interconnecting fret membranes were observed in the same basic arrangement as they appear in thin sections. Quantasome units, as previously described by other authors for other species, were detected. Portions of the peripheral reticulum and envelope were also observed. Swollen membranes, comparable to those observed when isolated plastids are placed in water, were frequent in the preparations. It can be assumed, then, that in any preparation of this nature the hydrophillic spaces will absorb a large amount of water, swelling the intramembranous spaces and giving the membranes the appearance of large vesicles which will appear as flattened sacs when dried on the electron microscope grids. As there is no indication of any quantasome pattern in these membranes it is assumed that the particle arrangement of these membranes was altered during the procedure. It was not possible to determine whether the membranes observed in the swollen vesicles belonged to the grana or frets. A change in the morphology of the membranes during the processing may be observed with the light microscope. Recognition of this change is frequently difficult in electron micrographs, consequently, membranes with similar appearance under the electron microscope may actually have arisen from different portions of the plastid membrane systems.