Ultrastructure, organization and cytochemistry of cytoplasmic crystalline inclusions in Origanum dictamnus L. leaf chlorenchyma cells.

In the cytoplasm of chlorenchyma cells in primary Origanum dictamnus leaves, rectangular prism-like crystals occur, which, as shown by pepsin digestion, are proteinaceous. In sections they usually show either a square lattice or striations running parallel to the short or long axis. In both cases the interspacings are estimated to be about 100 A, suggesting that the arrangement of the crystallographic planes possesses tetragonal symmetry. High magnifications of the crystalline inclusions together with analysis of their diffraction patterns showed that the striations are composed of double helices of protein macromolecules. In leaves 3-4 mm long, eroded crystals are often observed. When leaves are larger than 5 mm, no crystalline bodies can be identified in chlorenchyma cells. It is possible that they represent a storage form of protein, which is used later by the developing cells.