Biologists have speculated for years that modern land plants must have evolved from some group of aquatic green algae. Researchers like Dr. Linda Graham at the University of Wisconsin have presented morphological and developmental evidence that the four genera of charophyte algae, Chara, Nitella, Coleochaete, and Chaetosphaeridium, are most similar to land plants and are likely the closest living algal relatives of higher plants. In continuing studies of two of these genera, Dr. Graham is investigating new featurs of DNA quantity in cell nuclei, measuring cell size under varying environmental conditions, and testing for the occurrence of specialized compounds (callose and sporopollenin) common in land plants but rare to absent in most algae. Data from these studies will either corroborate or refute the idea that charophytes are close to land plants, and will also provide taxonomic characters aiding in the recognition of species within the genera Coleochaete and Chaetosphaeridium.
