Pollen morphology of six Achillea L. sect. Achillea (Asteraceae) species in Turkey

The pollen morphology of 48 specimens of 6 species (9 taxa) of the genus Achillea L. sect. Achillea (Asteraceae), A. nobilis L. subsp. neilreichii (A.Kern.) Formanek, A. nobilis subsp. densissima (O.Schwarz ex Bassler) Hub.-Mor., A. nobilis subsp. sipylea (O.Schwarz) Bassler, A. nobilis subsp. kurdica Hub.-Mor., A. filipendulina Lam., A. clypeolata Sm., A. coarctata Poir., A. biebersteinii Afan., and A. cappadocica Hausskn. & Bornm. distributed in Turkey were investigated using light (LM) and scanning electron microscopy (SEM). The pollen grains were oblate-spheroidal, prolate-spheroidal, subprolate and generally tricolporate, though at times tetracolporate or even pentacolporate. The size of the grains varied, ranging from 17.6 to 57.5 mu m on the polar axis mean and from 19.7 to 55.2 mu m on the equatorial axis mean. Their outline is oval, compressed oval, or circular in the meridional optical section and trilobulate or sometimes tetralobullate in the polar optical section. The structure of the exine is double tectate and mean exine thickness varied from 3 to 8.5 mu m. The pollen ornamentations are echinate in LM and echinate-microperforate and echinate-rugulate-microperforate in SEM. In conclusion, the species examined showed substantial variation in pollen characteristics, at both the interspecific and intraspecific levels.