Ultrastructure of barley aleurone cells as shown by freeze-etching.

Aleurone tissue from non-germinated or germinating barley seeds, as well as from isolated aleurone layers imbibed with water or gibberellic acid, was frozen directly in Freon and investigated by the freeze-etching technique. Aleurone grains remained spherical under all conditions, although the volume increased on hydration. They contained both protein crystalloids and globoids (phytin or lipid) embedded in the matrix. Globoids appeared to be membrane-enclosed. Spherosomes were evidently enclosed within a normal membrane, and they were in close contact with the membrane of aleurone grains, covering the surfaces of the latter. A highly-ordered particle structure was seen on some preparations of the plasmalemma. During germination no alterations were observed in membrane structure.