Browsing by Author "Helevecio De-Polli"

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    Confirmation of nitrogen fixation in two tropical grasses by 15N2 incorporation
    (1977) Helevecio De-Polli; Elichi Matsui; Johanna Dobereiner; Eneas Salati
    Intact soil cores containing plants of Paspalum notation or Digitaria decumbens were selected with the acetylene reduction method, and then exposed to 15N2 to confirm nitrogen fixation in tropical grass-bacteria associations. In a preliminary experiment with P. notatum 15N2 incorporation was slow but progressive during 24 h in roots but translocation to rhizomes and leaves ceased after 17 h. With improved assay chambers, enrichments of 0.151 and 0.563 15N atom % excess were obtained in roots of D. decumbens cv transvala and P. notatum systems respectively, after 3 days. Enrichments in rhizomes were similar to those of roots; however in the leaves only 8% of root enrichment was observed. The addition of sucrose to the soil doubled N2-fixation in roots in both grass species studied, but did not result in increased incorporation into the leaves of P. notatum.