Regulation of organic and inorganic nitrogen uptake in Scots pine (Pinus sylvestris) seedlings.
Plants possess regulatory mechanisms that enhance nitrogen (N) uptake under conditions of spatial and temporal variation in N availability. Study of regulatory mechanisms has focused almost exclusively on the uptake of inorganic N sources (i.e., ammonium (NH4+), nitrate (NO3-). Several lines of evidence, however, suggest that amino acids may constitute a potential source of N for a number of plant species, including conifers. In the present study, we investigated the uptake of amino acids and inorganic N in Scots pine (Pinus sylvestris L.) seedlings grown at different N concentrations. We compared the uptake rate of the individual N sources using U-[13C2], [15N]-glycine, U-[13C6], [15N4]-arginine, 15NH4, or 15NO3, and tested the short-term effect of N supply on the uptake rate of glycine, arginine and in field-grown Scots pine seedlings. Our data indicate that Scots pine seedlings can absorb substantial amounts of N in the form of intact arginine and glycine molecules. The data also suggest that Scots pine seedlings down-regulate their uptake of NH4+-N and arginine-N, but not of glycine-N in response to increased endogenous N concentrations.
Ohlund
Jonas
J
Umeå Plant Science Center, Department of Forest Genetics and Plant Physiology, SUAS, S-901 83 Umeå, Sweden. jonas.ohlund@genfys.slu.se
Näsholm
Torgny
T
D009584:Nitrogen / Q000378:metabolism*; D041605:Pinus sylvestris / Q000502:physiology*; D018517:Plant Roots / Q000502:physiology; D036226:Seedlings / Q000502:physiology*; D014197:Trees / Q000502:physiology*
D009584:Nitrogen