Studies on pollen morphology of<i>Rosaceae</i>

Abstract

Summary Light and scanning electron microscope studies of pollen representing genera from all tribes of the Rosaceae reveal a variety of form and sculpturing. All genera examined produce radially symmetric isopolar monads. Most genera in subfamilies Maloideae, Prunoideae, and Spiraeoideae produce tricolporate striate grains with large perforations in valleys between ridges. These tectate perforate grains have a chambered pore covered by arching ektexinal pore flaps. The ridge-and-valley pattern can vary from 1—long ridges parallel to the colpus, to 2—medium to long ridges looping near the poles, to 3—short weaving and crossing ridges. Striate perforate pollen occurs in tribes Dryadeae, Kerrieae, Roseae (operculate) and Rubeae of subfamily Rosoideae. in some Rubus species perforate and verrucate sculpturing occurs. Tribe Potentilleae (= Fragarieae) produces pollen with microperforations rather than typical perforations and most genera have an operculum. Coluria, Fallugia, Geum, Orthurus, and Waldsteinia of Dryadeae produce striate microperforate pollen, suggesting that they may belong in the Potentilleae. Filipendula (Ulmarieae) is prominently verrucate. Tuberculate perforate sculpturing occurs in Cercocarpus, Cowania, and Purshia suggesting a natural group distinct frcm the rest of the family. The diverse Poterieae (= Sanguisorbeae) has mainly tricolporate and some hexacolporate (Sanguisorba) grains all with an operculum. Some genera (Agrimonia group) have striate pollen, but most have microverrucae and perforations. Within the tribe, a distinctive group of mainly south hemispheric genera (Acaena, Cliffortia, Cowania, Hagenia, Leucosidea, Margyricarpus, Polylepis, Tetraglochin) has tricolporate perforate pollen, often with a short colpus, sculpturing of macroverrucae and rugulae covered by microverrucae. These pollen characteristics suggest a distinct evolutionary lineage.