Pollen morphology of Astragalus L. section Hololeuce Bunge (Fabaceae) in Turkey

Abstract Pollen morphology of 15 taxa belonging to the section Hololeuce Bunge of genus Astragalus L. species was investigated by light microscopy and scanning electron microscopy. Pollen slides were prepared using a Wodehouse technique. Measurements were based on 20 or more pollen grains per specimen. For scanning electron microscopy studies, dried pollen grains were transferred on aluminium stubs and coated with gold for 4 min in a sputter-coater. The pollen grains of Hololeuce taxa are radially symmetric and isopolar. The pollen grains of the taxa are prolate–spheroidal, subprolate or prolate with the polar axes 21.42–32.93 μm and the equatorial axes 17.13–28.26 μm. The pollen grains are operculate and trizonocolporate. Syncolporate. Colpi were usually long and narrow (Clt: 4.13–6.68 μm, Clg: 16.56–26.52 μm), subterminal, membrane granulate or verrucate. Pores were found to be longate or circular (Plg: 5.01–7.82 μm, Plt: 5.31–8.69 μm). Operculum membrane ornamentation verrucate, granulate, rugulate and reticulate. Pollen grains show reticulate, perforate polar section and perforate, reticulate, microreticulate, perforate–granulate, microreticulate–perforate, microrugulate–perforate, microrugulate–microreticulate, granulate–perforate, microreticulate–granulate at meridional sections. Exine is subtectate and has a thickness of 1.08–1.30 μm. Ectexine is thicker than endexine. Intine has a thickness of 0.5–0.68 μm. As result of this study some pollen characteristic as pollen shape, aperture type and ornamentations are shown to vary within the section Hololeuce. Especially pollen surface ornamentation on polar section and meridional section has systematic value to distinguish taxa from each other.