<P> There are also several nitrogen - fixing symbiotic associations that involve cyanobacteria (such as Nostoc): </P> <Ul> <Li> Some lichens such as Lobaria and Peltigera </Li> <Li> Mosquito fern (Azolla species) </Li> <Li> Cycads </Li> <Li> Gunnera </Li> </Ul> <Li> Some lichens such as Lobaria and Peltigera </Li> <Li> Mosquito fern (Azolla species) </Li>

Which molecule is not involved in the process of nitrogen fixation