02322nam a2200289 a 450000100080000000500110000800800410001910000170006024501370007726000620021430000100027649000230028650000350030952015390034465000160188365000130189965000100191265000170192265000100193965000160194965000160196565000090198165000130199065300100200365300100201365300090202316215101995-12-14       1983    bl uuuu  m   00u1 u    #d1 aDE-POLLI, H.  aNitrogenase activity in roots and stems of corn (Zea mays L.) cultivars and its response to nitrogen fertilizer and lime amendments.  aNew Brunswick: State University of New Jersey, Out.c1983  a132p.  aTese de Doutorado.  aOrientada por: Carlos A. Neira  aCorn (Zea mays L.) plants were assayed for nitrogenase activity (C2H" reduction) during early ear development. Hybrid corn and inbred lines were grown separately at two experimental fields in New Jersey. Acetylene-dependent ethylene production was observed a few hours after harvest by intact plants, root-soil cores, lower stem segments, and excised roots, all assayed under air and not preincubated. Incubation of excised roots at 1% (v/v) of O2 resulted in lower rates of C2H2 reduction as compared to 20% (v/v) of O2. The time course of C2H2 reduction by excised roots, assayed in air, was similar for all genotypes studied (two hybrids, eight inbreds, and a cross of corn x teosinte) and indicated that a long preincubation at reduced O2 was not absoluted requiredfor early detection of nitrogenase activity. Isolation of N2-fixing bacteria from within the roots and stems, together with the diurnal fluctuation of nitrogenase activity in response to day/night cycles, were indicative of a close association of N2 fixation with plant function. The data provided evidence for the occurrence of nitrogenase activity which was dependent upon indigenous N2-fixing bacteria, associated with corn plants growing in a temperate climate. A field experiment was conducted to evaluate the effects of cultivar, liming and N level on the nitrogenase activity (C2H2 reduction) associated with corn roots and stems and dependent upon indigenous N2-fixing bacteria. A significant positive effect (P = 0,01) of liming (5000 kg lime/ha) and a ...  afertilizers  anitrogen  astems  aFertilizante  aMilho  aNitrogenase  aNitrogênio  aRaiz  aZea Mays  aMaize  aRamos  aRoot