JXB Advance Access originally published online on July 4, 2006
Journal of Experimental Botany 2006 57(11):2651-2659; doi:10.1093/jxb/erl028
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RESEARCH PAPER |
Uptake, metabolism and distribution of organic and inorganic nitrogen sources by Pinus sylvestris

1Umeå Plant Science Center, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, S-90183, Umeå, Sweden
2Umeå Plant Science Center, Department of Plant Physiology, Umeå University, S-90183, Umeå, Sweden
To whom correspondence should be addressed. E-mail: torgny.nasholm{at}genfys.slu.se
Although an increasing number of studies show that many plant species have the capacity to take up amino acids from exogenous sources, the importance of such uptake for plant nitrogen nutrition is largely unknown. Moreover, little is known regarding metabolism and distribution of amino acid-N following uptake or of the regulation of these processes in response to plant nitrogen status. Here results are presented from a study following uptake, metabolism, and distribution of nitrogen from
Glu, or Ala in Scots pine (Pinus sylvestris L). In a parallel experiment, Ala uptake, processing, and shoot allocation were also monitored following a range of pretreatments intended to alter plant C- and N-status. Uptake data, metabolite profiles, N fluxes through metabolite pools and tissues, as well as alanine aminotransferase activity are presented. The results show that uptake of the organic N sources was equal to or larger than
uptake, while
uptake was comparatively low. Down-regulation of Ala uptake in response to pretreatments with NH4NO3 or methionine sulphoximine (MSX) indicates similarities between amino acid and inorganic N uptake regulation. N derived from amino acid uptake exhibited a rapid flux through the amino acid pool following uptake. Relative shoot allocation of amino acid-N was equal to that of
but smaller than for
Increased N status as well as MSX treatment significantly increased relative shoot allocation of Ala-N suggesting that
may have a role in the regulation of shoot allocation of amino acid-N.
Key words: Alanine, amino acid uptake, glutamic acid, regulation, transport
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