BOTANY VOLUME 3 - EVOLUTION AND SYSTEMATICS - 2007

11. SYSTEMATICS AND PHYLOGENY

11.2. Bacteria, fungi, plants

Fifth subkingdom: Glaucobionta

A distinguishing feature of the species in this small, highly distinct, yet important subkingdom is their Plastids, which contain phycobiliproteins as accessory pigments. Among the chlorophylls, chlorophylls a, c, and d are typical; chlorophyll b is absent. Starch is not deposited as a storage substance inside the plastids. In Glaucobionta, the eukaryotic level of Organization in Algae is achieved (see Box 11.5).

Sole division: glaucophytes (Glaucophyta)

This division, which includes only a few species of monadoid algae, is of great importance for understanding the evolution of photoautotrophic eukaryotes. In many respects, the METABOLISM/14.html">Chloroplasts still resemble blue-green algae; they have long been interpreted as endosymbiotic cyanobacteria and are termed cyanelles. They (or the chloroplasts) are still surrounded by a peptidoglycan wall, albeit a thin one; however, their Genome Size is only one-tenth of that of free-living cyanobacteria, thus corresponding to the Chloroplast Genome of other eukaryotes. There is also a significant similarity in Genome Organization between cyanelles and chloroplasts.

The blue-green plastids contain chlorophyll a (etc.) and, as accessory pigments, phycocyanin and several others in phycobilisomes, which are located inside the chloroplasts on unstacked thylakoids.

The sole Class of the division — Glaucophyceae — includes three freshwater algal genera (see Fig. 2.99), each with a single species. The Cells of Glaucocystis bear two rudimentary flagella and are no longer capable of active movement. Cyanophora has two flagella of unequal length.