Ultrastructural Studies on Plant Membranes
The most accepted hypothesis for the general organization of membranes is the fluid-mosaic model of Singer and Nicolson.1 In this model, membranes are viewed as a lipid bilayer with “integral” membrane proteins embedded in, as well as extending across, the lipid bilayer matrix. The model predicts that membranes can be asymmetrically organized with different lipids and proteins and amounts of each occurring in either half of the membrane. Also, Singer and Nicolson suggested that the lipid matrix was fluid with the lipid constituents as well as the proteins “floating” in this matrix, “freely” moving in the plane of the membrane. Thus, no long-range order or significant degrees of lateral heterogeneity as to the location of specific constituents would be expected in membranes unless constrained in place by extramembrane elements. In this paper, we examine the organization and lateral heterogeneity of plant membranes using electron microscopic methods.
KeywordsSalt Gland Lateral Heterogeneity Freeze Fracture Plant Membrane Cowpea Seed
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