Palynological investigation of some Euphorbia L. (Euphorbiaceae) taxa from Turkey using light and scanning electron microscopy

Euphorbia L., one of the largest genera of angiosperms, is represented by the subgenera Esula Pers. and Chamaesyce Raf. in Turkey. Subg. Esula is confined mainly to Eurasia, especially in the Mediterranean region, and has not yet been studied in detail palynologically. In the present study, the pollen morphology of 14 taxa belonging to the sections Helioscopia Dumort., Myrsiniteae (Boiss.) Lojac., Pithyusa (Raf.) Lázaro, Patellares (Prokh.) Frajman, Exiguae (Geltman) Riina & Molero, Paralias Dumort., and Esula (Pers) Dumort. of Euphorbia L. subg. Esula Pers. from European Turkey was examined using light and scanning electron microscopy. The pollen grains were found to be trizonocolporate, isopolar, radially symmetrical, medium in size, and oblate spheroidal and suboblate in shape. Ectoapertures were elongated colpi with distinct margins, widened at the equatorial region, and tapered at the ends; margo was present in all samples as a smooth exine surrounding the colpi. The endoapertures were lolongate pori with distinct costae. The exine was tectate-perforate. The ornamentation was perforate, microreticulate-perforate, microreticulate-perforate with rugulose, or microreticulate-perforate with a heterobrochate pattern. The sexine was generally thicker than the nexine, with some exceptions where the sexine was almost equal to the nexine. Pollen size, pollen shape, and exine ornamentation have taxonomic importance in distinguishing species; however, these features do not provide strong support for grouping or delimitating the taxa at the sectional level. RESEARCH HIGHLIGHTS: Pollen size, pollen shape, and exine ornamentation are taxonomically important for distinguishing Euphorbia species. The exine ornamentation was observed to be perforate, microreticulate-perforate, microreticulate-perforate with a rugulose pattern, and microreticulate-perforate with a heterobrochate pattern.