1. Institute of Molecular Plant Sciences, University of Edinburgh , Max Born Crescent, EH9 3BF, Edinburgh , UK
2. Institute of Botany, Czech Academy of Sciences , Dukelská 135, 37901 Třeboň , Czech Republic
3. Department of Biological Sciences, University of Bergen , Bergen , Norway
4. Department of Botany, Charles University , Benátská 2, 12801 Prague 2 , Czech Republic