title: Rhizospheric NO affects N uptake and metabolism in Scots pine (Pinus sylvestris L.) seedlings depending on soil N availability and N source.
abstract: We investigated the interaction of rhizospheric nitric oxide (NO) concentration (i.e. low, ambient or high) and soil nitrogen (N) availability (i.e. low or high) with organic and inorganic N uptake by fine roots of Pinus sylvestris L. seedlings by (15) N feeding experiments under controlled conditions. N metabolites in fine roots were analysed to link N uptake to N nutrition. NO affected N uptake depending on N source and soil N availability. The suppression of nitrate uptake in the presence of ammonium and glutamine was overruled by high NO. The effects of NO on N uptake with increasing N availability showed different patterns: (1) increasing N uptake regardless of NO concentration (i.e. ammonium); (2) increasing N uptake only with high NO concentration (i.e. nitrate and arginine); and (3) decreasing N uptake (i.e. glutamine). At low N availability and high NO nitrate accumulated in the roots indicating insufficient substrates for nitrate reduction or its storage in root vacuoles. Individual amino acid concentrations were negatively affected with increasing NO (i.e. asparagine and glutamine with low N availability, serine and proline with high N availability). In conclusion, this study provides first evidence that NO affects N uptake and metabolism in a conifer.
authors.affiliation: Institute of Forest Botany and Tree Physiology, Chair of Tree Physiology, University of Freiburg, Georges-Koehler-Allee 53/54, 79110 Freiburg, Germany. judy.simon@ctp.uni-freiburg.de
authors.forename: Judy
authors.initials: J
authors.lastname: Simon
authors.forename: Fang
authors.initials: F
authors.lastname: Dong
authors.forename: Franz
authors.initials: F
authors.lastname: Buegger
authors.forename: Heinz
authors.initials: H
authors.lastname: Rennenberg
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D001692:Biological Transport; D058440:Denitrification; D005973:Glutamine / Q000378:metabolism / Q000494:pharmacology; D038821:Mycorrhizae / Q000187:drug effects / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism* / Q000494:pharmacology; D058465:Nitrification; D009584:Nitrogen / Q000378:metabolism*; D041605:Pinus sylvestris / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology; D000644:Quaternary Ammonium Compounds / Q000378:metabolism / Q000494:pharmacology; D058441:Rhizosphere; D036226:Seedlings / Q000378:metabolism*; D012987:Soil / Q000737:chemistry
chemical_list: D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D012987:Soil; D000643:Ammonium Chloride; D005973:Glutamine; D009569:Nitric Oxide; D009584:Nitrogen