Plastid Replication in Vegetative Cells, Sporangia, Spores and Sporelings of Red Algae

Ultrastructural aspects of proplastid and chloroplast replication are described as seen in sections of vegetative cells, sporangia, released spores and sporelings of the red algae Palmaria palmata and Plumaria elegans. Proplastids in apical vegetative cells show internal thylakoid formation from peripheral thylakoids in both species, and proplastid formation by budding from mature chloroplasts has also been observed. Proplastid replication by fission has been occasionally observed, and genophore division in the stroma of proplastids. In vegetative cells, sporangia, spores and sporelings chloroplast formation from mature plastids can take place by elongation and fission, or by formation of a discrete group of thylakoids which become pinched off from the parent chloroplast, and by irregular expansions of the parent chloroplasts with subsequent multiple fission.