Pollen morphology of Degenia velebitica (Degen) Hayek and Sibiraea altaiensis (Laxm.) C. K. Schneid. subsp. croatica Degen – rare Croatian endemic plants from Velebit Mountains

Sa？etak Background and Purpose: Pollen can, as a means of genetic resource, contribute to conservation of endemic plants. Therefore we started with palynological study of endemic plants from refuges of the Alpine-Dinaric region and here present preliminary results on pollen morphology of two most famous representatives of Croatian endemic plants from Velebit Mts, Degenia velebitica and Sibiraea altaiensis subsp. croatica. Methods: Pollen samples from field collections were examined by the JEOL JSM-T 300 Scanning Electron Microscope in dry and hydrated state. For hydrated state, pollen grains were briefly rehydrated in water, dehydrated in acidified 2, 2-dimethoxypropane (DMP) and critical point dried in CO2. Dry pollen was mounted on stubs without further preparation. Both dry and critical point dried material was mounted on stubs and sputter coated with gold. Results: Pollen grains of Degenia velebitica are tricolpate, prolate and about 35 – 40 μm in diameter (longest axis). The colpi are extended and quite narrow. The exine ornamentation is reticulate homobrochate, lumina width is small (less than 2 μm in diameter). Dry pollen is prolate with infolded apertures. Pollen grains of Sibiraea altaiensis subsp. croatica are tricolporate, spheroidal to slightly oblate (hydrated condition) and about 25 μm in diameter. The apertures are quite smooth. Exine ornamentation is striate perforate consisting of coarse striae with perforations in the grooves. Dry pollen is prolate with infolded apertures. Conclusion: Evidence from pollen morphology of both taxa indicate a possibility of closer relationships with their relatives in the past. Despite this, both taxa developed their own palynological uniqueness and deserved conservation of their pollen samples