POLLEN WALL STRUCTURE USING A NEW STRIPPING SPUTTERING DEVICE FOR SCANNING ELECTRON-MICROSCOPY

A new method has been developed to elucidate pollen wall architecture by the separation of wall layers and the use of scanning electron micr oscopy (SEM). Separation of wall layers at natural boundaries, breakag e across the wall and metal-coating of the specimen have been achieved by controlled ramming of free scattered ions produced by a novel ''io n separating and coating - model A'' instrument. The stripping treatme nt reveals interfaces and cross profiles of pollen walls and the sputt ering treatment results in metal coating for examination with SEM. An advantage of the method is that it provides intact interfaces that are not eroded or damaged. The application of the method is exemplified b y SEM analyses of pollen grains of Gossypium hirsutum L., Zea mays L., Sesamum indicum L. and Brassica napus L. var, oleifera. Interfaces be tween the tectum, column, foot, nexine-2 and intine layers of the poll en wall were all portrayed in G. hirsutum and to a great part in the o ther species. In G. hirsutum, it was possible to document the attachme nt point of surface spines, the appearance of individual baculae and t he irregular labrum-operculum but regular inner labrum-aperture struct ure. No tectum was found in S. indicum. In all four species it was not possible to separate the intine from the sporoplast. The numbers of a pertures were 20, 1, 10-14 and 3 in G. hirsutum, Z. mays, S. indicum a nd B. napus, respectively. The dumbell-shaped arrangement of apertures in G. hirsutum, the gear-shaped oblate sporoplast of S. indicum and t he abundance of micropores on the intine of B. napus are characteristi c features.