1. Plant Cell Biology Research Group, Institute of General Botany, Justus-Liebig University, 35390 Giessen, Germany (J.B.H., A.C.U.F., F.G., A.J.E.v.B.); Transport Physiology Research Group, Department of Plant Ecology and Evolutionary Biology, University of Utrecht, 3584 CA Utrecht, The Netherlands (J.-K.v.A., F.K., A.J.E.v.B.); and Institute of Phytopathology, Justus-Liebig University, Interdiscip