DIVISION OF CHLOROPLASTS IN A GREEN-ALGA, PEDIASTRUM-DUPLEX

The division of chloroplasts in a green alga, Pediastrum duplex, was studied by electron microscopy. Cells were treated for observation with the freeze-substitution method. Fibrils, or fibrous belts, which we had observed previously at the dividing constrictions of chloroplasts in Trebouxia potteri were not visible in Pediastrum, even though the method of preparation was the same for both sets of samples. Microtubules (MTs) and the septum seem not to participate directly in the division of the single chloroplast in Pediastrum cells. Many thin fibrils, 7-20 nm in diameter, attached to, or protruding from, the surface of the dividing constriction were seen. These fibres were less densely distributed at the constrictions of non-dividing chloroplasts. It is suggested that these fibrils are involved in the divison of chloroplasts in Pediastrum duplex. © 1992 Annals of Botany Company.