It has been observed that not all species from the Anthocerotae class possess a pyrenoid state (Vaughn 1990). For example all genus of the multiplastidic Megaceros spp. and two uniplastidic species, Anthoceros fusiformis and Phaeoceros coriaceus, do not possess a pyrenoid-based CCM.
This is further borne out by carbon isotope studies where the delta values for Megaceros moandreus and Megaceros endivifolis (herbarium samples) show C3 responses. Whereas on-line measurements on Anthoceros crispus and Anthoceros agrestis (sporophyte) showed a C4-like response, although there is no evidence C4 or CAM biochemistry (pers com).
This situation raises some intriguing questions as to the evolutionary significance of the "no pyrenoid condition" in uniplastidic cells of some hornworts and liverworts that have assumed a C3 orientation.
This is further borne out by carbon isotope studies where the delta values for Megaceros moandreus and Megaceros endivifolis (herbarium samples) show C3 responses. Whereas on-line measurements on Anthoceros crispus and Anthoceros agrestis (sporophyte) showed a C4-like response, although there is no evidence C4 or CAM biochemistry (pers com).
This situation raises some intriguing questions as to the evolutionary significance of the "no pyrenoid condition" in uniplastidic cells of some hornworts and liverworts that have assumed a C3 orientation.