Nitrogenase Activity in Relation to Intracellular Organisms in Sphagnum Mosses

Electron microscopic studies of Sphagnum lindbergii (Schimp.) and S. riparium (Ångstr.) have revealed the presence of intracellular organisms such as blue‐green algae, green algae, bacteria and fungi. Nitrogenase activities of these Sphagnum mosses were found to be related mainly to the presence of intracellular Nostoc filaments. The appearance of nitrogen‐fixing blue‐green algae within bryophytes is thus not restricted to liverworts. The association is likely to be of ecological importance as it seems to occur in very acid habitats generally lacking blue‐green algae. Possible interrelations between the moss, the blue‐green algae and different types of bacteria are discussed.