The Fine Structure of the Trigger Hair in Venus's Flytrap

Abstract

Trigger hairs of Dionaea muscipula fixed in glutaraldehyde and OsO4 were prepared for study in the electron microscope. Electron micrographs of the active zone of the trigger hair reveal three regions in which the cells differ in size, shape, and cytoplasmic content. Each region contains large numbers of protein bodies and mitochondria with densely packed tubular cristae. Vacuole-like structures containing protein bodies or an anastomosing system of cisternae, or occasionally both, are also present. Found only in the indentation cells is a complex, whorled endoplasmic reticulum. A concentric lamellar arrangement of the endoplasmic reticulum around the vacuolar structures is often observed. The lateral walls of the indentation cells are disproportionately thick while end walls are thin. The basal walls of these cells contain many plasmodesmata. Plasmodesmata in the anticlinal and podium cells pass through constricted zones in the cell wall and are particularly numerous in the peripheral podium cells. The possible functional significance of these structures is discussed.