title: Nitrate and Ammonium Contribute to the Distinct Nitrogen Metabolism of Populus simonii during Moderate Salt Stress.
abstract: Soil salinity is a major abiotic stressor affecting plant growth. Salinity affects nitrification and ammonification in the soil, however, limited information is available on the influence of different N sources on N metabolism during salt stress. To understand the N metabolism changes in response to different N sources during moderate salt stress, we investigated N uptake, assimilation and the transcript abundance of associated genes in Populus simonii seedlings treated with moderate salt stress (75mM NaCl) under hydroponic culture conditions with nitrate (NO3-) or ammonium (NH4+). Salt stress negatively affected plant growth in both NH4+-fed and NO3--fed plants. Both NH4+ uptake and the total N concentration were significantly increased in the roots of the NH4+-fed plants during salt stress. However, the NO3- uptake and nitrate reductase (NR) and nitrite reductase (NiR) activity primarily depended on the NO3- supply and was not influenced by salt stress. Salt stress decreased glutamine synthetase (GS) and glutamate synthase (GOGAT) activity in the roots and leaves. Most genes associated with NO3-uptake, reduction and N metabolism were down-regulated or remained unchanged; while two NH4+ transporter genes closely associated with NH4+ uptake (AMT1;2 and AMT1;6) were up-regulated in response to salt stress in the NH4+-fed plants. The accumulation of different amino acid compounds was observed in the NH4+- and NO3-- fed plants during salt treatment. The results suggested that N metabolism in P. simonii plants exposed to salt enhanced salt resistance in the plants that were fed with NO3- instead of NH4+ as the sole N source.
authors.affiliation: Key Laboratory of Environment and Ecology in Western China of Ministry of Education, College of Forestry, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.|State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, 712100, Yangling, China.
authors.forename: Sen
authors.initials: S
authors.lastname: Meng
authors.affiliation: Key Laboratory of Environment and Ecology in Western China of Ministry of Education, College of Forestry, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.
authors.forename: Li
authors.initials: L
authors.lastname: Su
authors.affiliation: Key Laboratory of Environment and Ecology in Western China of Ministry of Education, College of Forestry, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.
authors.forename: Yiming
authors.initials: Y
authors.lastname: Li
authors.affiliation: Key Laboratory of Environment and Ecology in Western China of Ministry of Education, College of Forestry, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.
authors.forename: Yinjuan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Key Laboratory of Environment and Ecology in Western China of Ministry of Education, College of Forestry, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.|State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, 712100, Yangling, China.
authors.forename: Chunxia
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Environment and Ecology in Western China of Ministry of Education, College of Forestry, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.|State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, 712100, Yangling, China.
authors.forename: Zhong
authors.initials: Z
authors.lastname: Zhao
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D009566:Nitrates / Q000494:pharmacology*; D009584:Nitrogen / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D032107:Populus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D054712:Salinity; D012965:Sodium Chloride / Q000494:pharmacology*; D013312:Stress, Physiological / Q000187:drug effects*
chemical_list: D064751:Ammonium Compounds; D009566:Nitrates; D012965:Sodium Chloride; D009584:Nitrogen