Browsing by Subject "adaptation"

Many noble hardwood species of boreal and temperate climate zones will experience increased selection pressure for adaptive traits as climate change proceeds. This will cause shifts in the timing of phenological events such as budburst in spring. Shifts in phenology may disrupt interaction between species and their environment as well as interaction within and between species. Changes in the timing of annual life cycle traits may threaten species’ current fitness and potential to adapt to future climates. The rate and magnitude of phenological shifts will increase along with increasing temperatures. To adapt to changing environmental conditions, species need to possess adaptive variation in life cycle traits. In small and isolated populations at northern margins of species distribution, variation in adaptive traits is threatened by low genetic variation, low gene flow and genetic drift. To preserve the adaptive potential of noble hardwood populations in Finland, ex situ gene conservation collections are established where genetic resources are conserved as living trees. To characterize the adaptive potential currently present in Finnish gene conservation collections of European maple (A. platanoides L.), small-leaved linden (T. cordata Mill.) and European white elm (U. laevis Pall.), the amount of current phenological diversity should be evaluated. For this purpose, budburst progress in the collections was tracked by phenotypic observations on budburst phenological phases in relation to accumulating temperature. The data did not allow for analysis of variance between origin populations; therefore, a more conservative approach was chosen where conserved genetic resources were assessed by examining budburst differentiation between groups of origin populations. The level of differentiation in budburst temperatures is used as an indicator of spring phenological diversity to determine if the conserved origins are adapted to the same spring temperature range. No significant differentiation was found in the timing of budburst between groups of origins. Therefore, the conserved origins are presumed to be adapted to the same spring temperature range within their respective species distribution in Finland. However, low phenological diversity may magnify the threats imposed to these species by climate change. Genetic studies are recommended for deeper understanding of underlying genetic diversity and adaptive potential of the stored genetic resources.

In winter plants are exposed to harsh winter conditions with low temperatures being one of the major challenging factors. Traditionally winter has been considered a period unfavourable for plant growth and activity, but newer findings reveal higher levels of activity than previously assumed possible. Adaptations to different winter conditions are observed between species but also within species between populations which can be expressed in differing phenology between populations. Dormancy is a widespread phenomenon in the plant kingdom with major importance in plant evolution. Dormancy is considered to be present in seeds and buds of a wide spectre of plant groups, but asexual reproductive units like bulbils have been thought to lack the ability to undergo the phenomenon of dormancy. Findings suggest that a dormancy-like phenomenon can also be present in bulbils. Allium oleraceum is a bulb forming geophyte with a widespread distribution in Europe that grows on many differing habitats. The predominate form of reproduction in the species is the vegetative formation of bulbils. The wide distribution has led to adaptation to different environmental conditions, furthermore the species displays six levels of polyploidi partially differing in traits like ecology. The differences between cytotypes are regional and there are large intracytotytpic variations. In Finland tetra- and pentaploid populations have been reported, differing in their distribution patterns. The Finnish cytotypes exhibit differences in morphology but there is also evidence for ecological differences between the cytotypes. In addition, there is an atypical tetraploid population which differ significantly morphologically from other tetraploid populations. The objective of this master’s project was to examine the growth of bulbils from three different origins of Allium oleraceum. Another objective of the experiment was to give information on differences between the cytotypes in Finland, tetra- and pentaploids, but also the atypical tetraploid cytotype. Furthermore, I investigated whether the bulbils exhibit a dormancy-like phenomenon, with a special focal point on dormancy according to Vegis’ theory (1964). Earlier findings have shown considerable capability of growth during winter in Allium oleraceum, which is also examined in this project. The experiment included collected bulbils from two localities. Tetra- and pentaploid bulbils were collected from a mixed population of both cytotypes in Tvärminne, Hangö, and tetraploid bulbils were also collected from the atypical tetraploid population on Sveaborg, Helsingfors. Growth experiments were done outside and in growth chambers with controlled temperature and light conditions. The bulbils were planted outside in early autumn. Of each origin one group was kept outside during the entire winter, one group was put in growth chambers in December and one group was put in growth chambers in February to examine the effect of differing winter length on growth. During the experiment, the timing of growth onset in bulbs and leaf growth was followed up. The origins included in this project exhibited considerable differences. The pentaploid cytotype from Tvärminne had bulbils of greater size than the tetraploid cytotypes, between which there was only an indication of a difference. For the bulbils from the atypical tetraploid population growth onset took place early in the autumn and the vast majority of the bulbils started growing in a short period of time. For the two origins from Tvärminne the growth onset took place later and a considerable number of bulbils started growing in the spring. The tetraploid cytotype from Tvärminne exhibited earlier growth onset and a higher share of bulbils started growing in the autumn than the pentaploid cytotype from Tvärminne. In the growth chambers the differences between the three origins were not as obvious but the two cytotypes from Tvärminne were affected by the timing of the experiment more than the atypical tetraploid cytotype from Sveaborg. The observed differences between the origins in the experiment are thought reflect the different distribution patterns of the cytotypes and could hence be adaptations to different conditions. The atypical tetraploid population could be of Central European origin which would mean that it could have adaptations to mild winters which would explain the big difference between this origin and the two other origins. Between the two experiments in the growth chambers significant differences were observed. The growth was considerably greater in February than in December for all origins, especially in the midmost temperatures. The observed differences between the two experiments signifies that bulbils of Allium oleraceum exhibits a dormancy-like phenomenon and according to Vegis’ theory. In contrary to earlier findings, only little growth was observed during winter. The lack of considerable growth could be explained by the thick snow cover which made the amount of light that reached the plants very low which then led to little growth. The results from this project suggest that there are differences between the three different origins of bulbils included. Further studies are needed to find out if the observer differences are adaptations to local conditions or if there are differences on a higher level between the Finnish cytotypes.

Ecophysiology and ecology in plants are strongly affected by the conditions surrounding them. Adaptation aids plants to survive and to succeed in the prevailing conditions. Winter is a challenge to plants, particularly in northern latitudes and higher altitudes, because it exposes plants to cold and drought, for example. Plants survive from winter on species level with the help of genetic adaptations and as individuals also with the help of acclimation. Woodland strawberry (Fragaria vesca) has been observed to grow separate winter leaves. This allows it to continue photosynthesis in mild conditions during winter, thus improving its energy balance, and to start growing earlier than other species in the spring, which is beneficial in interspecific competition. Fragaria vesca is a species that has wide distribution in the northern hemisphere, and its genotypes are found from very different locations and conditions. However, adaptive traits such as producing a new set of leaves for winter can turn out to be a disadvantage if environmental conditions change rapidly. Climate change brings about changes that are difficult to predict, and these changes are advancing at a fast pace when compared to the developmental history of plants. The aim of this thesis was to study the effect of temperature on summer and winter leaf development, stolon formation and summer and winter leaf chlorophyll, flavonol and anthocyanin content in different Fragaria vesca genotypes. Leaf chlorophyll and secondary compound content give information about leaf development and stress reactions in plants. Plants are known to produce anthocyanins in order to protect the photosynthetic apparatus during chlorophyll recovery in leaf senescence. Anthocyanins are also produced as a response to low temperatures. Research increases knowledge of the ecophysiological and winter ecology-related processes in Fragaria vesca and in the commercially valuable Rosacea-family as well as provides information about the possible responses of these organisms to climate change. Material for the study consisted of twelve European Fragaria vesca genotypes, which had originally been collected from five countries: Norway, Finland, Germany, Italy and Spain. The genotypes had been collected from different latitudes, and they also expressed altitudinal differences. In this study, these genotypes were kept in two temperature treatments, warm (+16°C) and cold (+11°C/six weeks, after which +6°C/four weeks) at a greenhouse. Leaf development was studied by measuring summer and winter leaf middle leaflet width and length, and petiole length. Stolons from each plant individual were counted on a weekly basis and observations about stolon production in relation to the timing of summer leaf senescence and winter leaf development were made at the same time. Leaf chlorophyll and secondary compound content was measured with a Dualex-meter, which provided values for chlorophyll, flavonol and anthocyanin content. The underlying assumption was that cold temperature would induce winter leaf development and summer leaf senescence. The results show that there were differences in summer leaf size between genotypes. Winter leaves had differences between genotypes, but also within genotypes at different temperature treatments. Stolon count was lower and stolon production ceased slightly earlier in the cold treatment. Moreover, summer leaf chlorophyll content decreased in both treatments, but the summer leaves senesced earlier in the warm room. Summer leaf flavonol and anthocyanin values were generally higher in the cooler temperature treatment. Anthocyanins were also produced by winter leaves in the cooler temperature treatment. Based on the results, Fragaria vesca genotypes had differences related to their origin, but temperature also had an effect on winter leaf development, stolon production and the production of secondary compounds. The effect of cold temperature on the size of developing winter leaves was clear. In the cooler temperature treatment, the winter leaves were smaller than in the warmer treatment. The anthocyanin content of summer leaves was higher than in the winter leaves, and the summer leaf anthocyanin content was higher in the colder temperature treatment, where the stress related to the photosynthetic apparatus and low temperatures was combined. Nevertheless, lower temperature did not explain all the responses observed in the genotypes of the study, and thus it is likely that acclimation and winter leaf development in Fragaria vesca are affected by some other factor in addition to temperature, e.g. light regime. A possible continuation for this work would be to study the effect of light conditions or milder winters on winter leaf development in Fragaria vesca genotypes and on the physiology of the species.