Pollen Morphology of Some Galium L. (Rubiaceae) Taxa

Abstract

This study investigated the palynological characteristics of eleven Galium L. (Rubiaceae) taxa (G. setaceum, G. spurium subsp. spurium, G. aparine, G. rotundifolium, G. odoratum, G. rivale, G. incanum subsp. elatius, G. humifusum, G. verum subsp. verum, G. album subsp. pycnotrichum, and G. paschale) collected from different localities in Eskişehir Province, Türkiye. Pollen grains were examined using scanning electron microscopy (SEM). For each taxon, the polar axis (P), equatorial axis (E), P/E ratio, pollen shape, aperture number, colpus length (Cl), colpus width (Cw), and exine ornamentation were measured. Across the examined taxa, the smallest pollen grains were observed in G. paschale (P = 12.79 µm), whereas the largest were recorded in G. aparine (P = 28.20 µm). The equatorial axis (E) ranged from 8.70 to 19.90 µm, and the P/E ratio ranged from 1.25 to 2.20. Pollen grains were predominantly prolate in G. setaceum, G. spurium subsp. spurium, G. aparine, G. rotundifolium, G. odoratum, G. rivale, G. verum subsp. verum, and G. album subsp. pycnotrichum, whereas G. incanum subsp. elatius, G. humifusum, and G. paschale exhibited subprolate pollen. Aperture numbers ranged from penta- to nonacolpate, and exine ornamentation was consistently microechinate or microechinate–perforate. Although slight quantitative differences were observed among the examined taxa, the extensive overlap in pollen morphological characters indicates that palynological features alone provide limited taxonomic resolution for species-level discrimination within Galium.

Keywords

• Aperture morphology
• Exine ornamentation
• Palynotaxonomy
• SEM
• Pollen micromorphology

Supporting Institution

This research did not receive any specific grant from funding agencies.

Ethical Statement

This study does not involve experiments on humans or animals. Plant materials were collected and analyzed in accordance with relevant scientific and ethical standards. The author confirms that all procedures were conducted responsibly and ethically.

Thanks

The authors would like to thank Anadolu University / Department of Pharmaceutical Botany for their support and for providing laboratory facilities.

References

1. Abdel-Khalik, K., Abd El-Ghani, M.M., Elkordy, A.A., A palynological study of Galium L. (Rubiaceae) in Egypt and its systematic implication. Feddes Repertorium, 118 (7–8) (2007), 311–326. https://doi.org/10.1002/fedr.200711137
2. Başer, B., Akdeniz, S., Kürşat, M., Palynomorphological studies on some Asperula and Galium (Rubiaceae) taxa. Bitlis Eren Üniversitesi Fen Bilimleri Dergisi, 9 (2) (2020), 689–696. https://doi.org/10.17798/bitlisfen.652353
3. Duman, H., Doğan Güner, E., Özbek, F., Galium polatliense sp. nov. (Rubiaceae) from central Anatolia, Türkiye. Nordic Journal of Botany, 2025 (8) (2025), e04747. https://doi.org/10.1002/njb.04747
4. Ehrendorfer, F., Schönbeck-Temesy, E., Flora of Turkey and the East Aegean Islands. Vol. 7. In: Davis, P.H. (Ed.), Edinburgh University Press, Edinburgh, 1982, 767–850.
5. González-Tejero, M.R., Casares-Porcel, M., Sánchez-Rojas, C.P., Ramiro-Gutiérrez, J.M., Molero-Mesa, J., Pieroni, A., et al., Medicinal plants in the Mediterranean area: synthesis of the results of the project Rubia. Journal of Ethnopharmacology, 116 (2) (2008), 341–357. https://doi.org/10.1016/j.jep.2007.11.045
6. Goodman, A.M., Mechanical adaptations of cleavers (Galium aparine). Annals of Botany, 95 (3) (2005), 475–480. https://doi.org/10.1093/aob/mci038
7. Huysmans, S., Dessein, S., Smets, E., Robbrecht, E., Pollen morphology of NW European representatives confirms monophyly of Rubieae (Rubiaceae). Review of Palaeobotany and Palynology, 127 (3–4) (2003), 219–240. https://doi.org/10.1016/S0034-6667(03)00121-0
8. Perveen, A., Qaiser, M., Pollen flora of Pakistan–LIV. Rubiaceae. Pakistan Journal of Botany, 39 (4) (2007), 999–1015.

9. Pobedimova, E.G., Shishkin, B.K., Galium L. In: Flora USSR, Vol. 23, Izd. AN SSSR, Moskva–Leningrad, 1958, 287–381.
10. POWO, Plants of the World Online, Royal Botanic Gardens, Kew. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:325955-2 (accessed June 3, 2026).
11. Punt, W., Hoen, P.P., Blackmore, S., Nilsson, S., Le Thomas, A., Glossary of pollen and spore terminology. Review of Palaeobotany and Palynology, 143 (1–2) (2007), 1–81. https://doi.org/10.1016/j.revpalbo.2006.06.008
12. Ullah, T., Zafar, M., Ahmad, M., Alkahtani, J., Elshikh, M.S., Makhkamov, T., Yuldashev, A., Kilic, O., Sultana, S., Majeed, S., Mamarakhimov, O., Botirova, L., Nizomova, M., Integrating morpho-pollinic traits for systematic classification of rubiaceous species and conservation implications. Genetic Resources and Crop Evolution, 71 (8) (2024), 4465–4482. https://doi.org/10.1007/s10722-024-01917-4
13. Verstraete, B., De Block, P., Robbrecht, E., A survey of generic names in Rubiaceae (Gentianales) with notes on context and patterns in naming. Taxon, 74 (5) (2025), 1153–1171. https://doi.org/10.1002/tax.13360