Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Depletion of the heaviest stable N isotope is associated with NH4+/NH3 toxicity in NH4+-fed plants | Ariz et al. BMC Plant Biology 2011 11 83 http 1471-2229 11 83 BMC Plant Biology RESEARCH ARTICLE Open Access Depletion of the heaviest stable N isotope is associated with NH4 NH3 toxicity in NH4 -fed plants 1 s s 2 1 3 -4 Idoia Ariz Cristina Cruz Jose F Moran María B González-Moro Carmen García-Olaverri Carmen González-Murua3 Maria A Martins-Lougão2 and Pedro M Aparicio-Tejo1 Abstract Background In plants nitrate NO3- nutrition gives rise to a natural N isotopic signature Ỗ15N which correlates with the Ỗ15N of the N source. However little is known about the relationship between the Ỗ15N of the N source and the 14N 15N fractionation in plants under ammonium NH4 nutrition. When NH4 is the major N source the two forms NH4 and NH3 are present in the nutrient solution. There is a thermodynamic isotope effect between NH3 g and NH4 aq which drives to a different Ỗ15N. Nine plant species with different NH4 -sensitivities were cultured hydroponically with NO3- or NH4 as the sole N sources and plant growth and Ỗ15N were determined. Short-term NH4 NH3 uptake experiments at pH and which favours NH3 form were carried out in order to support and substantiate our hypothesis. N source fractionation throughout the whole plant was interpreted on the basis of the relative transport of NH4 and NH3. Results Several NO3--fed plants were consistently enriched in 15N whereas plants under NH4 nutrition were depleted of 15N. It was shown that more sensitive plants to NH4 toxicity were the most depleted in 15N. In parallel N-deficient pea and spinach plants fed with 15NH4 showed an increased level of NH3 uptake at alkaline pH that was related to the 15N depletion of the plant. Tolerant to NH4 pea plants or sensitive spinach plants showed similar trend on 15N depletion while slight differences in the time kinetics were observed during the initial stages. The use of RbNO3 as control discarded that the differences observed arise from pH detrimental effects. .
