Efectos de la nutrición fosforada en el metabolismo de nitrógeno de la soja no nodulada

two experiments were conducted under greenhouse conditions to study the influence of p deficiency on nitrogen nutrition of non-nodulated soybean. there was a reduction of n and p content in p deficient (p-) plants of almost 50% after 50 days. during this period, dry matter of these plants was reduced by 33%. nitrate reductase activity and shoot nitrate content were lower in p than in p+ plants. seventy five percent of nitrates in p- plants were in the roots. nitrate accumulation in roots would be due to the lower nitrate reductase activity in this organ and a reduced water flux to shoots. root nitrate concentration increases would cause a negative feedback which would reduce plant nitrate uptake.