Palynological investigations on some Hypericum taxa (Hypericaceae) growing naturally in Turkey

This study examined the detailed pollen morphological structures of sixteen Hypericum taxa (four endemic, twelve non endemic) including eight sections showing the natural distribution in Turkey: H. sect. Ascyreia (H. calycinum L.), H. sect. Heterophyllum (H. heterophyllum Vent.), H. Sect. Taeniocarpium (Hypericum confertum Choisy subsp. confertum, H. venustum Fenzl, H. linaroides Bosse), H. sect. Drosocarpium (H. montbretii Spach, H. bithynicum Boiss.), H. sect. Crossophyllum (H. adenotrichum Spach, H. orientale L.), H. sect. Olympia (H. olympicum L. subsp. olympicum), H. sect. Origanifolia (H. origanifolium Willd., H. avicularifolium Jaub and Spach subsp. depilatum (Freyn and Bornm.) Robson var. depilatum, H. avicularifolium Jaub. and Spach subsp. byzantinum) and H. sect. Hypericum (H. tetrapterum Fries, H. perforatum L., H. triquetrifolium Tura). These taxa were studied under light microscope and scanning electron microscope for the first time. Of the taxa studied, H. tetrapterum has the smallest pollen grains (on average 15.85–17.20 × 15.45–16.05 μm); and H. olympicum subsp. olympicum the largest grains (on average 22.90–23.10 × 21.40–22.10 μm). The pollen grains of 15 taxa are subprolate and one taxon is prolate-spheroidal. The regular pollen grains of all 16 taxa are 3-zonocolporate. Ornamentation is microreticulate; lumina regularly spaced in eight taxa, tectum perforatum; tectal perforations regularly spaced in seven taxa and tectum perforatum; and tectal perforations grouped together in one taxon. Endoaperture is cruciform porus, with short lateral and meridional extensions in ten taxa, cruciform porus, transversally elongated, with very small lateral extensions in one taxon and lalongate colpus in five taxa. Basic pollen types are ten taxa in type X, five taxa in type IV and one taxon in type II.