The Biology of Pomegranate Pollen: All about Formation, Morphology, Viability, Germination and Events relating to Sperm Nuclei

Abstract

Investigation of pollen biology (i.e. morphology, viability, germination capacity, development of pollen tube and sperm nuclei) of pomegranates, an andromonoecious species, was aimed in this study with the aid of microscopy. Pollens were collected from the Punica granatum L. cv. ‘Caner II’ at different phenological stages. Morphological features showed that the pollen is prolate with smooth exine surface. Viability was higher in the staminate flowers but germination capacity was better in the bisexuals. Pollen germination begins after it leaves the microsporangium. During pollen tube elongation, the pollen cytoplasm, vegetative nucleus and generative cells are transported within the pollen tube. Before entering the pollen tube, the generative cell undergoes mitosis and form two haploid generative cells. Differences in pollen viability and germination ratio of the flower types were found to be insignificant. Polar length was maximum (28.5 μm) in both sexual morphs and minimum (26.8 μm) in the perfect flower. The width of pollen grains ranged from 15.9 μm to 17.1 μm in both types. Perfect and functional male flowers had small pollen (15.9-27.3 μm) with grooves on the surface without perforations. The surface displayed regular continuities where it was between the protrusions. The surface of pollen grains from both of flowers was striate, with more parallel longitudinal ridges in functional male flower. The pollen from both sexes is about the same size. These findings not only provide information on basic features of pomegranate pollen and its pollination biology, but also can help understand breeding and decide strategies to develop better cultivars.

Keywords

• Punica granatum L.,Staminate,Pollen biology,Pollen tube formation

References

1. Barnabas, B., Fridvalszky, L., 1984. Adhesion and germination of differently treated maize pollen grains on the stigma. Acta Botanica Hungarica 30: 329-332.
2. Carol, A., Rudall, F., Paula, J., 2001. Pollen and anther characters in monocot systematics. Grana. 40 (1–2): 17-25. doi:10.1080/00173130152591840.
3. Derin, K., Eti, S., 2001. Determination of pollen quality, quantity and effect of cross pollination on the fruit set and quality in the pomegranate. Turkish Journal of Agriculture and Forestry 25: 169-173.
4. Engin, H., Unal, A., 2007. Examination of flower bud initiation and differentiation in sweet cherry and peach by scanning electron microscope. Turkish Journal of Agriculture and Forestry 31: 373-379
5. Engin, H., Gökbayrak, Z., 2015. Effect of epibrassinolide, gibberellic acid and naphthalene acetic acid on pollen germination of some pomegranate cultivars. COMU Journal of Agriculture Faculty 3(2): 19-25. (in Turkish)
6. Engin, H., Gökbayrak, Z., 2016. In vitro pollen viability and germination of bisexual and functional male flowers of some Turkıshpomegranate cultivars. Agriculture & Forestry 62 (4): 91-94.
7. Engin, H., Gökbayrak, Z., 2017. Micromorphology of pollen grains from bisexual and functional male flowers of pomegranate. AGROFOR International Journal 2(2): 40-46.
8. Engin, H., Hepaksoy, S. 2003. Determination of pollen germination of some pomegranate cultivars. Ege University Faculty of Agriculture Journal 40 (3): 9-16.

9. Erdtman, G., 1969. An Introduction to the Study of Pollen Grains and Spores. Copenhagen, Denmark: Munksgaard, pp. 486.
10. Erdtman, G., 1971. Pollen Morphology and Plant Taxonomy: Angiosperms. Hafner Publishing Company, New York, p.10-18
11. Gadže, J., Radunić, M., Petric, I.V., Ercişli, S., 2011. In vitro pollen viability germination and pollen tube growth in some pomegranate (Punica granatum L.) cultivars from Croatia and Bosnia and Herzegovina. Acta Scientiarum Polonorum Hortorum Cultus 10(3): 297-305.
12. Gökbayrak, Z., Engin, H., 2018. Effects of foliar-applied brassinosteroid on viability and in vitro germination of pollen collected from bisexual and functional male flowers of pomegranate, International Journal of Fruit Science 18(2): 226-230.
13. Gözlekçi, S., Kaynak, L., 2000. Investigations on pollen production and quality in some standards pomegranate (Punica granatum L.) cultivars. Options No: 42: 71-78.
14. Hancock, J.F., 2004. Plant Evolution and The Origin of Crop Species. 2nd ed. CABI Publishing, Cambridge, MA, USA.
15. Maiti, R., Gonzalez-Rodriguez, H., Ojha, E.R., 2016. Pollen biology and plant productivity: A review. In: Maiti R, Gonzalez Rodriguez H, Sergeevna Ivanova N. (editors). Autoecology and Ecophysiology of Woody Shrubs and Trees: Concepts and Applications. 1st ed., John Wiley & Sons, Ltd.
16. Sangma, D., Singh, D., 2017. Pollen viability and germination studies of pomegranates cultivars and wild germplasm accessions. International Journal of Agricultural Sciences 9(9): 3930-3932.
17. Shangshang, Y., Zhaohe, Y., Yanlei, Y., Xueqing, Z., Lijuan, F., Lingling, H., Feng, Z., 2015. Pollen morphology of pomegranate (Punica granatum L.) from different eco-geographical populations in China. Acta Horticulturae 1089: 269-277.
18. Varasteh, F., Arzani, K., 2009. Classification of some Iranian pomegranate (Punica granatum) cultivars by pollen morphology using scanning electron microscopy. Horticulture Environment and Biotechnology 50(1): 24-30.
19. Yang, S., Yuan, Z., Li, Y., Li, Q., Yin, Y., Feng, L., Zhao, X., 2013. Biological characteristics of pollen germination of ‘Taishanhong’ pomegranate. Scientia Silvae Sinicae 49: 48-53.
20. Yin, Y.L., Yuan, Z.H., Feng, L.J., Zhao, X., Tao, J. 2011. Comparison of pollen ultrastructural morphology among pomegranate (Punica granatum L.) cultivars in Shandong province. Acta Horticulturae Sinica 38: 955-962.
21. Zhao, X.G., Xiao, L., 1996. A study on pollen morphology of Punicaceae from China. Acta Botanica Boreali Occidentalia Sinica 16: 52-55.