1. Czech Advanced Technology and Research Institute, Palacky University , Šlechtitelů 27, 78371 Olomouc , Czech Republic
2. Centre of the Region Haná for Biotechnological and Agricultural Research, Department of Genetic Resources for Vegetables, Medicinal and Special Plants, Crop Research Institute , Šlechtitelů 29, 78371 Olomouc , Czech Republic
3. Isotope Laboratory, Institute of Experimental Botany, The Czech Academy of Sciences , Vídeňská 1083, CZ-14220, Prague , Czech Republic