are photosynthetic protists related to plants?
1 They are photosynthetic using chlorophyll a. 2  Their closest relatives are the green algae and land plants. 3  Like the cyanobacteria, they use. 4  as antenna pigments. 5  phycoerythrin (which makes them red) and. 6  phycocyanin. 7  They do not have the eukaryotic 9+2 flagellum.8  Some are used as food in coastal regions of Asia. The red algae are almost exclusively marine. 2  Some are unicellular but most are multicellular. 3  Approximately 6000 species have been identified. 4  They are photosynthetic using chlorophyll a. 5  Their closest relatives are the green algae and land plants.