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JXB Advance Access originally published online on January 8, 2007
Journal of Experimental Botany 2007 58(5):929-934; doi:10.1093/jxb/erl247
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© 2007 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)

RESEARCH PAPER

Accumulation of ammonium in Norway spruce (Picea abies) seedlings measured by in vivo 14N-NMR

H Aarnes1,*, AB Eriksen1, D Petersen2 and F Rise2

1Department of Biology, University of Oslo, PO Box 1066, Blindern, N-0316 Oslo, Norway
2Department of Chemistry, University of Oslo, PO Box 1033, Blindern, N-0315, Oslo, Norway

* To whom correspondence should be addressed. E-mail: halvor.aarnes{at}bio.uio.no

14N-NMR and 31P-NMR have been used to monitor the in vivo pH in roots, stems, and needles from seedlings of Norway spruce, a typical ammonium-tolerant plant. The vacuolar and cytoplasmic pH measured by 31P-NMR was found to be c. pH 4.8 and 7.0, respectively, with no significant difference between plants growing with ammonium or nitrate as the N-source. The 1H-coupled 14Formula resonance is pH-sensitive: at alkaline pH it is a narrow singlet line and below pH 4 it is an increasing multiplet line with five signals. The pH values in ammonium-containing compartments measured by 14N-NMR ranged from 3.7 to 3.9, notably lower than the estimated pH values of the Pi pools. This suggests that, in seedlings of Norway spruce, ammonium is stored in vacuoles with low pH possibly to protect the seedlings against the toxic effects of ammonium Formula or ammonia (NH3). It was also found that concentrations of malate were 3–6 times higher in stems than in roots and needles, with nitrate-grown plants containing more malate than plants grown with ammonium.

Key words: Ammonium, cytoplasmic pH, in vivo 14N-NMR, in vivo 31P-NMR, malate, organic acids, Picea abies (L.) Karst., vacuolar pH

Received 26 July 2006; Revised 17 October 2006 Accepted 26 October 2006


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