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The role of pollen in the changing environmental conditions of Scots pine
No full textRapid change in climate is challenge for the adaptation of forest trees in the future. In wind pollinated tree species pollen mediated long distance gene flow may provide alleles that are (pre)adapted to a future climate.
In order to examine the long distance pollen flow in Scots pine (Pinus sylvestris L.), we measured the amount and viability of airborne pollen and flowering phenology in central, northern, and northernmost Finland during four years. Viable airborne pollen grains were detected during female flowering and before local pollen shedding in all study sites. The situation when there was nonlocal pollen in the air lasted from one to four days depending on the year and study site. The amount of nonlocal airborne pollen varied also between years and study sites, the total amount of nonlocal viable pollen in the air was 2.3% from all detected viable pollen grains.
The effect of pollen origin on seeds siring ability was studied with artificial pollination experiments. Pollen genotypes originating from southern Finland sired 76% and 48 % of the analysed seeds in competition studies where both pollen origin were introduced simultaneously into the female strobili.
We examined the importance of arrival order of pollen grains in to the strobili in a study where pollen genotypes of different origin were introduced in two hours interval. Northern genotypes sired 76% of the analysed seeds when it was injected first, but in the "southern first" experiment both pollen types sired equal amount of seeds. The first pollen grain in the pollen chamber do not always fertilizes the ovum, instead there likely is more complex way of competition between pollen grains.
To examine chemically mediated pollen-pollen interactions we conducted in vitro germination experiment where different pollen genotypes had chemical but not physical contact. Both positive and negative effects of interactions were found. We found highly negative effects in germinability of northern pollen grains when they were germinating with southern pollen, and increase in the germinability of southern pollen.
There were no variation in the size of the dry pollen grains between pollen origins, and minor variation between different genotypes. After hydration and germination northern pollen grains were larger than southern pollen. Pollen genotypes having high hydration rates had low germinability and tube growth rate, however, germinated pollen grains were larger in size than nongerminated. This supports the suggestion that the early germination and growth of pollen tube is dependent on pollen storage materialsand less dependent on water intake and hydration.
Long distance pollen movements and good competition ability of southern pollen makes gene flow possible, although rising temperature and timing of pollen movements may affect pollen competition and the amount of gene flow.Tuulipölytteisen männyn sopeutumista ilmaston lämpenemiseen voi helpottaa valmiiksi tuleviin olosuhteisiin sopeutuneista populaatioista siitepölyn mukana kulkeutuvat geenit. Edellytyksenä tälläisen geenivirran syntymiseen on siitepölyn kaukokulkeutuminen, sekä kaukokulkeutuneen siitepölyn hyvä kilpailukyky paikallista siitepölyä vastaan. Myös siitepölyn kaukokulkeutumisen ja kohdepaikan emikukinnan on osuttava samaan aikaan.
Siitepölyn kaukokulkeutumisen mahdollisuutta ja ajoitusta emikukinnan suhteen tutkimme tarkkailemalla kukintaa, mittaamalla siitepölymääriä ilmassa ja testaamalla ilmasta kerätyn siitepölyn itävyyskykyä Korpilahdella, Rovaniemellä ja Kevolla vuosina 1997-2000. Ennen paikallista hedekukintaa ilmassa olevan itämiskykyisen männyn siitepölyn määrä oli 2.3% kaikesta ilmasta kerätystä männyn siitepölystä ja emikukinnoista 7,5% oli avoinna. On mahdollista että erityisesti ensimmäisinä aukeavat männyn emikukat pölyttyvät useiden satojen kilometrien päästä lähtöisin olevalla siitepölyllä.
Eteläisen ja pohjoisen siitepölyn kilpailukykyä tutkimme kilpailuristeytysten ja molekyylibiologisten isyystestausten avulla. Kahdessa eri tutkimuksessa eteläiset siitepölyt hedelmöittivät 76% ja 48% tutkituista siemenistä.
Ensimmäisenä kukkaan saapuneen siitepölyhiukkasen mahdollisesti saamaa kilpailuetua tutkimme pölyttämällä emikukkia ensin eteläisellä siitepölyllä ja kahden tunnin kuluttua pohjoisella pölyllä, ja päinvastoin. Pohjoiset siitepölyt saivat etumatkasta huomattavan kilpailuedun, kun taas eteläinen pöly ei siitä hyötynyt. Kun pölytys tehtiin eteläisen ja pohjoisen pölyn sekoituksella, pohjoisen saama kilpailuetu katosi.
Siitepölyjen kemiallisen vuorovaikutuksen mahdollisuutta selvitimme idättämällä eri siitepölyerät nesteitä läpäisevän kalvon eri puolilla. Havaitsimme sekä positiivista että negatiivista vuorovaikutusta: eteläiset siitepölyt itivät kilpailutilanteessa paremmin ja pohjoiset huonommin kuin kontrolli-idätyksissä.
Itämisaikaisen lämpötilan vaikutusta siitepölyn itämiseen ja siitepölyputken kasvuun tutkittiin idättämällä siitepölyeriä + 15ºC ja + 20ºC lämpötiloissa kasvatusliuoksessa. Siitepölyjen itävyys ja siitepölyputken kasvu oli nopeampaa + 20ºC:ssa kuin + 15ºC:ssa, pohjoiset siitepölyt hyötyivät korkeammasta lämpötilasta enemmän kuin eteläiset pölyt.
Siitepölyn kaukokulkeutuminen ja eteläisen pölyn kilpailukykyisyys mahdollistavat geenivirtauksen männyllä. Lämpötilan nousu ja kaukokulkeutumisen ajoitus voivat kuitenkin vaikuttaa siitepölykilpailuun ja sitä kautta geenivirran määrään.ei saavutettav
Männyntaimien syysväritys kertoo taimien kestävyydestä
No full textJulkaisusatoaSeloste artikkelista: Pulkkinen, P., Varis, S., Jaatinen, R., Leppänen, A. & Pakkanen, A. 2011. Increasing survival and growth of Scots pine seedlings with selection based on autumn coloration. Silva Fennica 45(4): 573–581
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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