Thylakoid membranes in sunflower and in other plants.

In the early ontogenesis of the sunflower plastids, the thylakoids show a particular staining, They are characterized by a wide, electron-transparent central region and by a thin electron-dense line on the stroma's side to which, possibly, an analogous dark line corresponds on the intrathylakoidal side of the compartment. The latter line is difficult to see because of the electron density of the intrathylakoid compartment. The peculiar membrane appearance persists for a long time, and sometimes it is observed in plastids with well-arranged grana and abundant starch. Therefore we can assume that the photosystems can be inserted into such membranes. The presence of chlorophyllous pigments on "lightly stained membranes" also seems to be suggested by the cotyledonous etioplasts that show prolamellar bodies with a paracrystalline lattice. As the LS membranes are present in plants belonging to very different families, we may assume that they are not a peculiarity, but on the contrary, are widely distributed in nature. © 1978 Academic Press, Inc.