EFFECTS OF PETUNIA CYTOPLASMIC MALE-STERILE (CMS) CYTOPLASM ON THE DEVELOPMENT OF STERILE AND FERTILITY-RESTORED P-PARODII ANTHERS

The developmental defects causing cytoplasmic male sterility in Petuni a parodii are described in isonuclear fertile, sterile, and fertility- restored plants using both light- and scanning electron microscopy. Th e aberrant development of the sporogenous tissue and tapetal layer cau sed by the cytoplasmic male sterile cytoplasm in both Petunia hybrida and P. parodii nuclear backgrounds is similar in onset and progression . The degeneration of the sporogenous tissue and tapetal layer of ster ile anthers is first apparent late in meiosis and results in highly ab normal sterile sporogenous tissue by tetrad stage of fertile anthers. The stomium and endothecium do not show major developmental difference s between fertile and sterile anthers, but the inner connective tissue of sterile anthers contained calcium crystals not found at high abund ance in fertile anthers. Ovoid bodies containing magnesium and phospho rus were seen only in the vascular bundles of fertile anthers. Materia l prepared for the scanning electron microscope by freeze drying showe d better retention of fragile morphological features, while critical-p oint drying permitted examination of nonvolatile structures, such as c ell walls.