Pollen–pollen interactions in Pinus sylvestris

Abstract

Direct pollen–pollen interactions can influence pollen fertilization ability when pollen from different donors and origins germinate on the same flower. In this study, in vitro germination tests were used to study direct pollen–pollen interactions in Scots pine (Pinus sylvestris L.). Pollen from southern (S, latitude 61° N) and northern (N, latitude 68° N) origins was germinated separately and in pairs at two temperatures (16 and 20°C), and pollen germination percentages and pollen tube lengths of the samples were analysed. The observed pollen performances of the two-donor pollen mixtures were compared with the mean performances of the pure pollen samples germinated in isolation. The significant difference between the observed and expected pollen performances indicated pollen–pollen interactions. Among S×S mixtures, only negative pollen–pollen interactions (= interference) were detected, while only positive interactions were found among N×N mixtures. Both types of interaction were substantially more frequent at the lower temperature. In general, direct pollen–pollen interactions during in vitro germination were rather infrequent and are not likely to have substantial influence on fertilization abilities in vivo in seed orchards or in natural forest stands of Scots pine. However, direct pollen–pollen interactions can be more pronounced among certain genotypes, which should be considered in artificial crossing experiments using pollen mixtures.

Keywords:

• In vitro germination
• pollen interference
• pollen tube growth
• Scots pine
• seed orchard

Acknowledgments

We would like to thank the two anonymous reviewers and Drs Åsa Lankinen and Roosa Leimu for their constructive comments on the earlier versions of the manuscript, Aulis Leppänen for collecting the pollen material, Tuuli Pakkanen for the help in measuring the pollen performances, Dr Juha Lappi from the Finnish Forest Research Institute for the help in statistical testing and Michelle Barrett for kindly checking the language. This study was financially supported by the Finnish Forest Research Institute, Academy of Finland and Niemi Foundation.

Notes

Parantainen, A. ¹ and Pasonen, H.-L. ² (¹Aerobiology Unit, Department of Biology, Section of Ecology, University of Turku, FI-20014, Finland, and ²Department of Applied Biology, P.O. Box 27, University of Helsinki, FI-00014, Finland). Pollen–pollen interactions in Pinus sylvestris.

Additional information

Notes on contributors

Annika Parantainen

Parantainen, A. 1 and Pasonen, H.-L. 2 (1Aerobiology Unit, Department of Biology, Section of Ecology, University of Turku, FI-20014, Finland, and 2Department of Applied Biology, P.O. Box 27, University of Helsinki, FI-00014, Finland). Pollen–pollen interactions in Pinus sylvestris.