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 observationwith the freeze-substitution method. Fibrils, or fibrous belts,which we had observed previously at the dividing constrictionsof chloroplasts in Trebouxia potteri were not visible in Pediastrum,even though the method of preparation was the same for bothsets of samples. Microtubules (MTs) and the septum seem notto participate directly in the division of the single chloroplastin Pediastrum cells. Many thin fibrils, 7–20 nm in diameter,attached to, or protruding from, the surface of the dividingconstriction were seen. These fibres were less densely distributedat the constrictions of non-dividing chloroplasts. It is suggestedthat these fibrils are involved in the divison of chloroplastsin Pediastrum duplex. Cell wall, chloroplast division, freeze-substitution, intermediate fibres, Pediastrum duplex, transmission electron microscopy