ULTRASTRUCTURE AND DEVELOPMENT OF OIL IDIOBLASTS IN ANNONA-MURICATA-L

The ultrastructure and development of oil idioblasts in the shoot apex and leaves in Annona muricata L. are described, and three arbitrary developmental stages are distinguished: cells in which no additional cell wall layers have been deposited against the initial primary cell wall, possessing an electron-translucent cytoplasm and distinct plastids which lack thylakoids (stage 1); cells in which a suberized layer has been deposited against the primary wall (stage 2, the cytoplasm resembles that of the preceding stage), and cells in which an additional inner wall layer has been deposited against the suberized layer, which increases in thickness with development (stage 3). In this stage an oil cavity is formed, surrounded by the plasmalemma, and attached to a bell-like protrusion of the inner wall layer, the cupule. A complex membranous structure occurs next to the cupule. Smooth tubular endoplasmic reticulum (ER), appearing as linearly arranged tubules, and groups of crystalline bodies with an almost hexagonal outline are present. The final stage was further subdivided into three subgroups (a, b, c) based on the extent of the oil cavity, its contents, and the composition of the cytoplasm, and increasing thickness of the inner wall layer. The oil is probably synthesized in the plastids, released into the cytoplasm, and then passed through the plasmalemma surrounding the oil cavity. © 1990 Annals of Botany Company.