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- Bochenek, Grazyna, 1977, et al.
(författare)
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Annual growth of male and female individuals of the Common Ash (Fraxinus excelsior L.)
- 2010
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Ingår i: Plant Ecology and Diversity. - : Informa UK Limited. - 1755-0874 .- 1755-1668. ; 3:1, s. 47-57
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Tidskriftsartikel (refereegranskat)abstract
- Background: In general, females of woody dioecious plants are expected to grow more slowly than males because of the high cost associated with fruit bearing. Yet wind-pollinated species may invest relatively heavily in male reproduction, and various compensatory mechanisms can offset incurred costs, therefore the apparent growth of genders might be similar over a longer period of time. Any cost-related disparities are expected to be most pronounced in mast flowering years, when female reproductive resource demand is highest. Aims: We aimed to investigate gender-related response in relation to the cost of reproduction, and as a function of climate. Methods: Using dendrochronology techniques and analysing growth parameters at the branch level, we compared long-term and seasonal growth of male and female Fraxinus excelsior trees. Results: There was no observed decline in trunk growth of either of the genders over a 55-year period, but male and female trees had distinguishable annual growth patterns. The tree-ring widths of both genders were smaller in masting years than in other years. The difference between genders could be explained by their response to different climatic variables: females are more sensitive to spring frost and drought in early summer, while male growth depends more on late summer conditions. Conclusions: Vegetative development and flowering create a feedback system that minimises the cost of reproduction and assures that expenses are covered. Hence, growth differences between genders may be related to their phenological and physiological disparities rather than reproductive cost differences per se.
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| 2. |
- Bochenek, Grazyna, 1977, et al.
(författare)
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First Come, First Served: Delayed Fertilization Does Not Enhance Pollen Competition in a Wind-Pollinated Tree, Fraxinus excelsior L. (Oleaceae)
- 2011
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Ingår i: International Journal of Plant Sciences. ; 172:1, s. 60-69
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Tidskriftsartikel (refereegranskat)abstract
- Under natural conditions pollen vectors act stochastically, and the order in which pollen arrives can influence seed paternity. In a number of wind-pollinated taxa, however, fertilization does not occur immediately. It has been proposed that delayed fertilization promotes pollen competition by providing a “fair start” for pollen tubes. To test this hypothesis we compared paternity after simultaneous and consecutive pollinations with multiple donors in Fraxinus excelsior. Additionally, we investigated pollen tube growth in naturally pollinated flowers. Under natural conditions pollen grains arrived on the stigma one by one, and their mean number reached 6 after 10 d of anthesis. A pollen tube from the first-arriving pollen grain entered the style after 24 h and reached the base on the second day following pollination. Fertilization by nuclei from the same first-arriving pollen tube occurred after stigma necrosis about 3 wk later. Paternity tests confirmed that pollen applied first in the experimental pollinations had an overwhelming advantage over pollen applied 24 h later. As delayed fertilization does not play a role in prezygotic selection in this species, flowering phenology might be more important for paternity success than pollen tube growth performance.
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| 3. |
- Bochenek, Grazyna, 1977
(författare)
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Reproductive Biology and Population Genetics of Common Ash (Fraxinus excelsior L.)
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Common Ash, Fraxinus excelsior L. (Oleaceae) is a wind-pollinated, wind-dispersed, deciduous tree, commonly occurring throughout Central and Northern Europe. The thesis addresses several questions concerning reproductive biology and factors influencing the genetic richness of ash stands. The breeding system is characterised in morphological terms as polygamous. However, individuals can be described as male, or seed producing hermaphrodites and females. The gender-related differences in vegetative growth were investigated on the branch level using dendrochronological techniques. The radial growth of male and female individuals turned out to be similar in a long-term perspective, but males invested more in building up their crown biomass. Genders responded also to different climatic variables. To determine the conditions for male gametophyte competition, a series of controlled pollinations were conducted and the pollen tube growth in naturally pollinated pistils was observed. As many other temperate trees, fertilization is delayed in Fraxinus and the pollen tube growth is arrested in the style. The results showed that the trait does not play any role in prezygotic selection in this species. The order of pollen grain arrival and, thus, flowering phenology was more important for paternity success than pollen tube growth performance. Furthermore, the functional breeding system of F. excelsior was examined. Hermaphrodite individuals were shown to have very low male fecundity and so could be classified as functionally female. To test the effect of maternal flowering phenology on mating distances and genetic variability of their progeny nuclear microsatellite markers were employed on early and late flowering individuals. Additionally the influence of genetic population structure on the level of biparental inbreeding was discussed. Microsatellite markers were used also to examine the level of inbreeding and allelic richness in the commercial stock of ash seed available for reforestation. Results from both works confirmed that neutral genetic variation in Fraxinus excelsior is high and that the level of inbreeding is very low the allelic diversity of an individual seed family may vary depending on flowering synchrony of neighbouring trees. Collection of seed from limited number of trees should be avoided; also the genetic diversity and structure of seed sources should be assessed when obtaining planting material for forest restoration
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