Nitrogen uptake and metabolism in Populus x canescens as affected by salinity.
External salinization can affect different steps of nitrogen (N) metabolism (ion uptake, N assimilation, and amino acid and protein synthesis) depending on the inorganic N source. Here, we assessed the net uptake of N supplied as nitrate or ammonium and N assimilation (combining metabolite analyses with molecular biological approaches) in grey poplar (Populus x canescens) plants grown under saline (75 mM NaCl) and control conditions. The specific (micromol N g(-1) dry weight fine roots h(-1)) and total plant (micromol N per plant h(-1)) N net uptake rates, total plant N content, total plant biomass and total leaf protein concentration were reduced under saline conditions when plants were supplied with ammonium. In both nutritional groups, salt treatment caused pronounced accumulation of soluble N compounds in the leaves. The mRNAs of genes coding for enzymes catalyzing rate-limiting steps of both proline synthesis and degradation (delta-1-pyrroline-5-carboxylate synthase and proline dehydrogenase) as well as for NADH-dependent glutamate synthase were accumulated under saline conditions. Whereas under control conditions the plant N status seemed to be superior when ammonium was supplied, the N balance of ammonium-fed plants was more severely affected by salt stress than that of plants supplied with nitrate. Possible metabolic implications of stress-related accumulation of particular amino acids are discussed.
Dluzniewska
P
P
Institute of Forest Botany and Tree Physiology, University of Freiburg, Georges-Koehler-Allee 53/54, D-79110 Freiburg, Germany.
Gessler
A
A
Dietrich
H
H
Schnitzler
J-P
JP
Teuber
M
M
Rennenberg
H
H
D018533:Biomass; D018506:Gene Expression Regulation, Plant; D009584:Nitrogen / Q000378:metabolism*; D032107:Populus / Q000254:growth & development / Q000378:metabolism*; D012965:Sodium Chloride / Q000378:metabolism*
D012965:Sodium Chloride; D009584:Nitrogen