ORIGINAL ARTICLE Responses of the pea (Pisum sativum L.) leaf metabolome to drought stress assessed by nuclear magnetic resonance spectroscopy Adrian J. Charlton Æ James A. Donarski Æ Mark Harrison Æ Stephen A. Jones Æ John Godward Æ Sarah Oehlschlager Æ Juan L. Arques Æ Mike Ambrose Æ Catherine Chinoy Æ Philip M. Mullineaux Æ Claire Domoney Received: 14 May 2008 / Accepted: 28 August 2008 Ó Springer Science+Business Media, LLC 2008 Abstract While many compounds have been reported to change in laboratory based drought-stress experiments, little is known about how such compounds change, and are significant, under field conditions. The Pisum sativum L. (pea) leaf metabolome has been profiled, using 1D and 2D NMR spectroscopy, to monitor the changes induced by drought-stress, under both glasshouse and simulated field conditions. Significant changes in resonances were attrib- uted to a range of compounds, identified as both primary and secondary metabolites, highlighting metabolic path- ways that are stress-responsive. Importantly, these effects were largely consistent among different experiments with highly diverse conditions. The metabolites that were present at significantly higher concentrations in drought- stressed plants under all growth conditions included proline, valine, threonine, homoserine, myoinositol, c-aminobutyrate (GABA) and trigonelline (nicotinic acid betaine). Metabolites that were altered in relative amounts in different experiments, but not specifically associated with drought-stress, were also identified. These included glutamate, asparagine and malate, with the last being present at up to 5-fold higher concentrations in plants grown in field experiments. Such changes may be expected to impact both on plant performance and crop end-use. Keywords Pea leaf metabolome Á Drought-stress Á NMR spectroscopy 1 Introduction A major limitation to yield and quality in many crop spe- cies is water availability throughout or at critical times in the growing season (Parry et al. 2005; Morison et al. 2008). In the face of a mild soil water deficit, plants can maintain photosynthesis and turgor for a short period (Boyer 1970; Morison et al. 2008). However, with exten- ded periods of negative soil water potential, plants stop growing, show decreased photosynthesis and initiate a series of measures that ensure their survival and/or re-direct resources to flowering and seed production (Boyer 1970; Lawlor and Cornic 2002; McKay et al. 2003; Forster et al. 2004; Morison et al. 2008). Across the spectrum of mild to severe drought conditions, plants employ a range of specific responses to minimise water loss or increase the rate of water uptake (Morison et al. 2008). These include regulation of stomatal conductance (Davies et al. 2002; Buckley 2005), maintenance of cell turgor and osmotic adjustment (Zhang et al. 1999), and protection of cellular macromolecules, membranes and enzymes from oxidative damage (Shen et al. 1997; Kranner et al. 2002; Srivalli et al. 2003; Quan et al. 2004; Munne ´-Bosch and Lalueza 2007; Hura et al. 2007). Maintenance of tissue water content by altering developmental processes is also important and includes altered canopy morphology (Davies Electronic supplementary material The online version of this article (doi:10.1007/s11306-008-0128-0) contains supplementary material, which is available to authorized users. A. J. Charlton (&) Á J. A. Donarski Á M. Harrison Á S. A. Jones Á J. Godward Á S. Oehlschlager Central Science Laboratory, Sand Hutton, York YO41 1LZ, UK e-mail: adrian.charlton@csl.gov.uk J. L. Arques Á M. Ambrose Á C. Chinoy Á C. Domoney John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK e-mail: claire.domoney@bbsrc.ac.uk P. M. Mullineaux Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK 123 Metabolomics DOI 10.1007/s11306-008-0128-0