1 Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark.
2 Department of Molecular Biology and Genetics, University of Aarhus, Forsøgsvej 1, 4200 Slagelse, Denmark.
3 UR1268 Biopolymères Interactions Assemblages, INRA, F-44316 Nantes, France.
4 Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
5 Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark. Electronic address: abl@plen.ku.dk.