原始色素体生物（Archaeplastida）即泛植物，是真核生物的主要群体。包括红藻、绿藻、陆生植物（有胚植物）及少量合称为灰胞藻的生物。除了植物以外，这个组的其他生物只具有部份的植物特性，例如红藻和灰胞藻没有植物必须的叶绿素b的。

所有这些生物体的色素体（叶绿体等）有两层膜包围，表明了这些生物体是直接内共生蓝藻而进化来的。其它的真核生物的色素体包有3或4层膜，显示它们是通过内共生绿藻或红藻而获得的色素体。这也是本类生物称之为"原始色素体"生物的由来。

研究证据表明，红藻、绿藻与陆生植物明确形成了单系群，拥有共同起源。

The Archaeplastida (or Plantae sensu lato) are a major group of eukaryotes, comprising the red algae (Rhodophyta), the green algae, and the land plants, together with a small group of freshwater unicellular algae called glaucophytes. The chloroplasts of all these organisms are surrounded by two membranes, suggesting they developed directly from endosymbiotic cyanobacteria. In all other groups besides the amoeboid Paulinella chromatophora, the chloroplasts are surrounded by three or four membranes, suggesting they were acquired secondarily from red or green algae.