SUBSTRUCTURE OF SPORE AND POLLEN GRAIN EXINES IN LYCOPODIUM, ALNUS, BETULA, FAGUS AND RHODODENDRON - INVESTIGATION WITH ATOMIC-FORCE AND SCANNING-TUNNELING-MICROSCOPY

We have used atomic force microscopy and scanning tunnelling microscop y to extract new information about the substructure of the Alnus, Betu la, Fagus Lycopodium and Rhododendron pollen grain exine. Our scans of exines using atomic force microscopy and scanning tunnelling microsco py reveal somewhat similar substructures for Lycopodium spores and pol len of Alnus, Betula, Fagus and Rhododendron. They show Various levels of alignment and clustering of substructure components. Except for Al nus, which showed polygonal clustering of spheroids and weak alignment , there is pronounced alignment of helical units. In Betula, Fagus, Ly copodium and Rhododendron the subunits appear to be helical or perhaps consisting of elongated spheroids, these spheroids are however arrang ed in a way that suggest that they are part of a helical structure. Th e diameter of these helical subunits range from 10-15nm in Fagus, 20-2 5 nm in Lycopodium, 35-90 nm in Rhododendron up to 70-120 nm in Betula . Our preparations graded from intact or fractured fresh pollen to pol len that was acetolyzed, chemically fixed and epoxy resin embedded. Wh ile our knowledge of the exact radial/lateral orientation of most of o ur scans is less than perfect there were in all cases substructures or cross connections of exine units. We found results from scanning and transmission electron microscopy to be helpful in understanding images from Atomic Force- and Scanning Tunnelling Microscopy.