Dinitrogen fixation (C2H2‐reduction) bydalbergia sissooandleucaena leucocephalawith native Pakistani Rhizobia strains

Abstract

Abstract Dalbergia sissoo Roxb. ex DC. and Leucaena leucocephala (Lam.) de Wit form effective symbiotic associations with native rhizobia strains from the arid plains of Pakistan. The rhizobium associated with L. leucocephala was fast growing and acid producing, whereas that associated with D. sissoo was slow growing and alkali producing. L. leucocephala rhizobia had an acetylene‐reducing potential of 0.38 μmol C2H4 plant−1hr−1, whereas the activity of D. sissoo rhizobia was only 0.16 μmol C2H4 plant−1hr−1. The specific nitrogenase activity (C2H2 reduction) of L. leucocephala rhizobia nodules was 20.8 μmol C2H4 g−1hr−1, whereas that D. sissoo nodules was 27.9 μmol C2H4 g−1hr−1. Strong correlations were observed between the number of nodules, nodule dry weight, shoot dry weight and acetylene reducing activity in both tree species.