1. Institute of Plant Nutrition, University of Hannover, Herrenhäuser Strasse 2, 30419 Hannover, Germany (M.M.F.-C., W.J.H.); Department of Applied Genetics, University of Hannover, Herrenhäuser Strasse, 30419 Hannover, Germany (H.-P.B.); and Laboratoire de Spectrométrie de Masse Bioorganique, Unité Mixte de Recherche 7509, 25 rue Becquerel, F-67087 Strasbourg cedex 2, France (C.L.-G., A.V.)