Archaeplastid in the context of "Glaucophyte"

The evolution of plants has resulted in a wide range of complexity, from the earliest algal mats of unicellular archaeplastids evolved through endosymbiosis, through multicellular marine and freshwater green algae, to spore-bearing terrestrial bryophytes, lycopods and ferns, and eventually to the complex seed-bearing gymnosperms and angiosperms (flowering plants) of today. While many of the earliest groups continue to thrive, as exemplified by red and green algae in marine environments, more recently derived groups have displaced previously ecologically dominant ones; for example, the ascendance of flowering plants over gymnosperms in terrestrial environments.

There is evidence that cyanobacteria and multicellular thalloid eukaryotes lived in freshwater communities on land as early as 1 billion years ago, and that communities of complex, multicellular photosynthesizing organisms existed on land in the late Precambrian, around 850 million years ago.

Rhodelphis is a single-celled archaeplastid that lives in aquatic environments and is the sister group to red algae and possibly Picozoa. While red algae have no flagellated stages and are generally photoautotrophic, Rhodelphis is a flagellated predator containing a non-photosynthetic plastid. This group is important to the understanding of plastid evolution because they provide insight into the morphology and biochemistry of early archaeplastids. Rhodelphis contains a remnant plastid that is not capable of photosynthesis, but may play a role in biochemical pathways in the cell like heme synthesis and iron-sulfur clustering. The plastid does not have a genome, but genes are targeted to it from the nucleus. Rhodelphis is ovoid with a tapered anterior end bearing two perpendicularly-oriented flagella.