The process of conversion of nitrogen to a combined form is catalyzed by a complex
metalloenzyme nitrogenase. It catalyzes the reduction of dinitrogen to ammonia in an ATPdependent
manner. Recently, though in limited extent, evidences have been found regarding
the nitrogen fixation in non leguminous crops. The total understanding of both leguminous
and non-leguminous nitrogen fixation in the crops and the cause of limited nitrogen fixation is
reviewed here. The various achievements in manipulating the host plant and the
microorganism to improve the yield of nitrogen fixation are also discussed in this review.
Key words: nitrogenase, nif genes, St nitrogenase, uptake hydrogenase, chloroplast,
protoplast, para nodules, ureide