Abstract
The freeze fracture method was used to study changes in membrane particles during the development from prothylakoids to grana thylakoids in Phaseolus plastids. In the present study, the fact of the transformation of PTs to primary thylakoids via perforated membranes was confirmed. Particles, 70-80Å in diameter, were located on both PF and EF fracture faces of PTs. These may be considered core particles. As the thylakoids develop in the light, 70-80Å particles grew up to 165Å in diameter. However, except for the grana thylakoids, the total number of particles per unit area remained nearly constant throughout the development of monolayered thylakoids including PTs and stroma thylakoids. On illumination, it appears that the size increase of core particles in PTs proceeds in stepwise way. This indicates that the enlargement of particles occurs by the association of core particles with other ones.
