Freeze-fracture studies on barley plastid membranes IV. Analysis of freeze-fracture particle size and shape

Abstract

The shape and size of freeze-fracture particles of rotary shadowed barley thylakoids were measured and plotted as three-dimensional histograms. It was not possible to resolve discrete sub-populations of particles, distinct in shape or size, on any of the fracture faces examined. It is concluded that much of the variation in particle shape and size was due to plastic deformation during freeze-fracturing, and to shadowing artefacts. The suggestion is made that EFs particles are uniformly sized in vivo. Particle size measurements can be useful, however, in making comparisons between different fracture faces and between corresponding faces of wild-type and mutant membranes, as long as the limitations of the technique are considered. The differences between corresponding faces of wild-type andchlorina-f2 thylakoids were found to be statistically significant for the EFs. ESs and PF faces.