POLLEN MORPHOLOGY OF TEUCRIUM (LABIATAE) AND ITS TAXONOMIC VALUE

Pollen morphology of 29 Mediterranean species, belonging to seven sections of the genus Teucrium L., has been investigated by scanning electron and light microscopy. The exine is tectate-perforate, but variations in exine sculpturing make it possible to distinguish four pollen types; verrucate, granulate, suprareticulate and pollen grains with an intermediate sculpturing composed of short, discontinuous supratectal ridges. Exine sculpturing type, pollen size and the density of supratectal elements seem to have a systematic value. Verrucate sculpturing is found in the basal groups of Teucrium, such as sections Teucrium and Teucropsis. This sculpturing type is associated with large sparsely verrucate pollen grains, particularly in section Teucrium subsection Teucrium. The section Scorodonia subsection Stachyobotrys can be distinguished by its suprareticulate sculpturing, a character that is clearly associated with the bilabiate or pseudo-bilabiate species. The intermediate sculpturing is found mainly in the unilabiate sections with subactinomorphic calyx such as Polium, Chamaedrys and Montanum. Spinularia is characterised by medium to large pollen grains with a low granule density.