Pollen–pollen interactions inPinus sylvestris

Abstract

Direct pollen Á/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 Á/pollen interactions in Scots pine (Pinus sylvestris L.). Pollen from southern (S, latitude 618 N) and northern (N, latitude 688 N) origins was germinated separately and in pairs at two temperatures (16 and 208C), 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 Á/pollen interactions. Among S)/S mixtures, only negative pollen Á/pollen interactions (0/ 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 Á/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 Á/pollen interactions can be more pronounced among certain genotypes, which should be considered in artificial crossing experiments using pollen mixtures.

Interactions during in vitro germination of Scots pine pollen

“…Results from earlier in vitro studies suggest that direct interactions among pollen of different genotypes occur in Scots pine (Parantainen and Pasonen 2004). We found both positive and negative effects when we germinated northern and southern genotypes in the permeable insert with competing pollen in a well.…”

“…We found in two cases a statistically significant difference in the germination percentage between the control and competition, one positive and one negative. Also Parantainen and Pasonen (2004) found positive and negative effects in studies with Scots pine. Marshall et al (1996) found a negative effect on germination in wild radish (Raphanus sativus) when pollen from two different donors was mixed before application rather than being placed separately on either of the two halves of the stigma.…”

“…Combined pollen mixtures from different sources have been germinated in vitro to remove the possible effect of maternal tissue (Pasonen and Käpylä 1998;Lankinen and Skogsmyr 2002;Parantainen and Pasonen 2004). In Scots pine the germination percentages of mixed pollen were higher than expected in three and lower than expected in nine out of 45 different mixtures (Parantainen and Pasonen 2004). In silver birch (Betula pendula Roth.…”

“…Snow andSpira 1991, Walsh andCharlesworth 1992;Lankinen 1999, 2002) focus on pollen traits such as tube growth rate rather than direct pollen-pollen interactions. Combined pollen mixtures from different sources have been germinated in vitro to remove the possible effect of maternal tissue (Pasonen and Käpylä 1998;Lankinen and Skogsmyr 2002;Parantainen and Pasonen 2004). In Scots pine the germination percentages of mixed pollen were higher than expected in three and lower than expected in nine out of 45 different mixtures (Parantainen and Pasonen 2004).…”

The extent of south-north pollen transfer in Finnish Scots pine

“…Pollen competition is well studied in angiosperm species (rev. Skogsmyr and Lankinen 2002;Bernasconi 2003), but only few experiments have been done with coniferous species (Owens and Simpson 1982, Webber and Yeh 1987, Parantainen and Pasonen 2004, Varis et al 2008, Pulkkinen et al 2009, Varis et al 2009). Artificial crosses with Scots pine pollen mixtures has either identified a competitive advantage for pollen from southern Finland (Pulkkinen et al 2009) or no difference among pollen strains (Varis et al 2008).…”