Chloroplast structure and starch grain production as phylogenetic indicators in the lower Rhodophyceae

Abstract

The position of starch grain production, the shape of the starch grains and the depth to which the pyrenoid is embedded in the chloroplast are used as indicators of evolution in the lower Rhodophyceae. A cell with cytoplasmic allantoid starch grains encasing the pyrenoid and no thylakoids between the chloroplast envelope and the pyrenoid is considered to be evolutionarily primitive. A cell with oval starch grains not associated with the pyrenoid and with a pyrenoid deeply embedded in the chloroplast is thought to be evolutionarily advanced. A polyphyletic origin of the Porphyridiales is discussed.