Nitrogenase activity associated with leaf,root, and rhizosphere soils in an Indian tropical forest

Summary N₂ fixation (acetylene reduction assay) by phylloplane microorganisms was measured in dominant and co-dominant plant species growing in a tropical rain forest. No significant acetylene reduction was recorded with intact leaf samples. Azotobacter sp., Beijerinckia sp., Derxia sp., and Klebsiella pneumoniae were isolated as phylloplane N₂-fixing bacteria. Azospirillum lipoferum was only isolated from soil samples containing the roots of Poaceae. Nitrogenase activity was recorded in culture derived from the roots and rhizosphere soil samples, although low acetylene reduction activity indicates that these associations did not provide large amounts of N to the systems studied.