02465nam a2200361 a 450000100080000000500110000800800410001910000220006024501150008226000430019730000110024050000200025152015450027165000170181665000130183365000150184665000150186165000120187665000170188865000130190565000140191865000160193265000140194865000230196265300080198565300140199365300360200765300060204365300080204965300290205765300110208665300060209711913792024-04-18       1987    bl uuuu  m   00u1 u    #d1 aPEREIRA, P. A. A.  aImprovement of N2 fixation in common bean (Phaseolus vulgaris L.) at different levels of available phosphorus.  aMadison: University of Wisconsinc1987  a151 p.  aTese Doutorado.  aPhosphorus is one among several factors which affects N2 fixation, and besides N, a principal yield-limiting nutrient in many regions of the world. Since the host plant is an essential partner in symbiosis, knowledge of host genotypic variability for N2 fixation at different levels of P availability will be useful when breeding cultivars for enhanced N2 fixation. The objective of this study was to investigate the possibility of obtaining common bean (Phaseolus vulgaris L.) lines which can fix large amounts of N2 under different levels of available phosphorus. Experiments were conducted in a growth room using a sand-alumina system which was reproducible and well suited for studying N2 fixation under different levels of available P and in the field where a low-Nsoil was chosen. In the growth room studies, P availability strongly affected plant growth and traits related to N2 fixation. However, no beneficial response was detected on the growth of the 14 common bean lines with addition of mycorrhiza. Competition for P between nodules and pods was observed at latter stages of growth, although other factors also contributed to a decline in nitrogenase activity and reduced nodule dry weight during the reproductive stage. Nodules were the plant part richest in phosphorus, and nodule dry weight was affected more than nodule number by limiting P supply, perhaps indicating that growth of the nodules was the primary factor limiting N2 fixation at low P levels. Generally no significant interaction was detected for P levels.....  akidney beans  anitrogen  aphosphorus  aAdubação  aFeijão  aFertilizante  aFósforo  aMicorriza  aNitrogênio  aNutriente  aPhaseolus Vulgaris  aFBN  aFixação  aFixacao biologica de nitrogenio  aN  aNBF  aNitrogen fixing bacteria  aNível  aP