Rhodophyta

Abstract

The Rhodophyta (red algae) owe their colour to the presence of excess of r-phycoerythrin in their chromatophores and this red pigment masks the colour of other photosynthetic pigments. The Rhodophyta are characterized by six main features: (1) the flagellated motile stages are totally absent; (2) the sexuality is highly specialized; the male gamete, called spermatium, is motionless and at the time of fertilization is passively transported to and lodged on the trichogyne of the female carpogonium; also, there are distinct post-fertilization developments not found in any other algal phyla; (3) chlorophyll-d, biliproteins (r-phycoerythrin and r-phycocyanin) and the xanthophyll taraxanthin are the characteristic pigments; besides, the chromatophores generally contain chlorophyll-a, α and β carotenes, lutein, zeaxanthin, neoxanthin and rarely other xanthophylls; (4) the reserve foods are floridean starch and galactoside floridosides and these do not accumulate within the chromatophore but outside it, in the cytoplasm; (5) the cell wall contains polysulphate esters of carbohydrates in addition to cellulose and pectin; and (6) the transverse walls in multicellular forms are generally provided with pits which permit cytoplasmic connection between adjacent cells.