Growth and Maintenance of an Embryogenic Cell Culture of Daylily {Hemerocallis) on Hormone-free Medium

The division of chloroplasts in Trebouxia potteri was studiedby electron microscopy. At the beginning of chloroplast division,vesicles with fine fibrils (FVs) and ER attach to the isthmusof the chloroplast. Then, filaments appear around the isthmusparallel to the direction of constriction and seem to contractin order to decrease the diameter of the isthmus. It is suggestedthat the FVs are involved in the formation of the filamentsand that the ER is involved in the contraction of the filaments.At the final stages of the division of the chloroplast, thefilaments decompose. FVs are partially surrounded and decomposedby lysosomal sheets. For the next cycle of division of the chloroplast,the recovery of substances from decomposed filaments by functionalFVs seems a realistic possibility. chloroplast division, division apparatus, division cycle, transmission electron microscopy, Trebouxia potteri     

The Synchronous Division of Dictyosomes at the Premitotic Stage

The number and distribution pattern of dictyosomes in cellsof a green alga,Closterium ehrenbergii, were examined by fluorescencemicroscopy. Dictyosomes absorbed the fluorescent dye, DiOC6(3) intensely, and strongly radiated fluorescent light. Dictyosomeswere distributed in the cytoplasm along the longitudinal chloroplast-ridges.They began to divide synchronously at a premitotic stage whenthe chloroplast started to divide, and duplicated in numberbefore the cell divided by a transverse septum. Approximatelythe same number of dictyosomes entered each daughter cell. Thedictyosomes never migrated freely in the cytoplasm but migrateda short distance after division. Cell cycle; Closterium ehrenbergii; division of dictyosomes; fluorescence microscopy; Golgi apparatus; vital staining