The aquatic fern Azolla maintains a well-known symbiotic relationship with the cyanobacterium Anabaena azollae. This nitrogen-fixing microbe lives within specialized cavities in the fern's leaves. In rice fields, this partnership acts as a highly effective biofertilizer: the Anabaena fixes atmospheric nitrogen into ammonia, which the Azolla then provides to the rice crop, potentially increasing yields by up to 50%.

──────────────────────────────────────────────────────────────────────────────────────────