1. Laboratory of Plant Cell Biology, Department of Botany, Institute of Biosciences, University of S�o Paulo, Rua do Mat�o, 277, room 107, S�o Paulo, SP 05508-090, Brazil
2. USDA Forest Service, Northern Research Station, 271 Mast Rd, Durham, NH 03824, USA
3. Department of Biological Sciences, University of New Hampshire, Durham, NH 03824, USA