Photoproduction of molecular hydrogen by a plant-algal symbiotic system.

The rapidly growing water fern Azolla, which contains a nitrogen-fixing blue-green algal symbiont, has been studied as a possible system for photoproduction of molecular hydrogen. When this plant is grown on a combined nitrogen supply, photochemically generated hydrogen can be diverted through the algal nitrogenase system, which serves as a source of molecular hydrogen generated from water. This symbiosis has several advantages as a possible biological energy conversion system.