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Browsing by master's degree program "Kasvitieteen maisteriohjelma"

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  • Liu, Zhenzhen (2022)
    Woodland strawberry (Fragaria vesca) is a perennial herb in the Rosaceae family with dimorphic leaves, summer and winter leaves, adapted to seasonal climate. Woodland strawberry produces a new set of leaves in spring that are photosynthetically active throughout the summer season (summer leaves), and the leaves senescence in autumn when they are replaced by a new set of leaves (winter leaves). The winter leaves retain photosynthetic capacity under the snow cover throughout the winter season, which prolong the photosynthetic period of the species. With the world-wide climate warming, the thickness of winter snow is decreasing, which can affect overwintering and spring phenology of plants. This thesis focuses on springtime ecophysiology and phenology of the senescing winter leaves and the formation of new summer leaves of woodland strawberry genotypes of different European origin. The 15 different genotypes of woodland strawberry are from Iceland, Italy and Norway, and they originate from different environments that are geographically separated from each other, so the populations are genetically distinct. In this study, these genotypes were kept at two different overwintering sites, coastal site at the Åland islands with mild temperatures, and continental site in Lammi with a persistent snow cover. According to the results all 15 genotypes showed earlier development of the summer leaves and earlier senescence of winter leaves in the group with Åland as overwintering site than in the group with Lammi. Another important finding is that the first summer leaves produced in spring begun to senesce shortly after they are fully developed and were replaced by later formed summer leaves. Specifically, the dates of summer leaf formation, flowering and stolon production were advanced, and the dates of winter leaf senescence were also advanced. The value of different leaf types to chlorophyll fluorescence was also lower at the Åland site. Therefore, it can be concluded that overwintering conditions have an effect on the subsequent phenological development in spring. In the context of global climate change, the spring development of woodland strawberry will be earlier, and the senescence of winter leaves will also be earlier.
  • Zhou, Quan (2020)
    Leaf senescence is a developmental and physiological phase in plants to end leaf development. Environment factors such as drought stress, extreme temperature, and pathogen threat and internal factors including age and reactive oxygen species induce leaf senescence. Some phytohormones such as jasmonic acid and salicylic acid play a key function in cell death in plants. WRKY transcription factors is known as one of the largest transcription factor family in plants which regulates a variety of plants processes. WRKY75 which belong to WRKY transcription factors has shown multiple functions in plant development like regulation of Pi starvation responses and root development and flowering. In my thesis, I focused on the role of WRKY75 in senescence and stress responses. WRKY75 was identified as a positive regulator of cell death in Arabidopsis. WRKY75 can promote salicylic acid biosynthesis by promote transcript levels of SID2 and also cause hydrogen peroxide accumulation by suppressing the transcription of CAT2. Hydrogen peroxide and salicylic acid can promote WRKY75 transcription at the same time. To evaluate the function of WRKY75 transcription factor in SA signalling and cell death, three lesion mimic mutants acd5, cat2, dnd1 and their corresponding wrky75 double mutant were used. Interestingly, no different phenotypes were found between acd5, cat2, dnd1 and their corresponding wrky75 double mutants in cell death and hydrogen peroxide accumulation detection in Arabidopsis leaves. Meanwhile, marker genes transcription levels were not different in both short day and long day growth condition. However, different phenotypes were observed in botrytis infection. Based on these results, we formed a hypothesis that gene redundancy could influence genetic characterization of WRKY75. To overcome this problem, SRDX-WRKY75 chimeric repressor transgenic lines were generated. The SRDX domain act as a dominant negative regulator to suppress WRKY75 target genes. In future research, these new lines can be used to test transcript levels for putative WRKY75 target genes.
  • Amin, Al (2021)
    Wood development is a significant process with both financial as well as natural perspectives. Trees and wood are of highly significance in Finland where a huge part of the gross national income devises from the forestry area. Ecologically and commercially the Norway spruce (Picea abies) is one of the most common tree species in Europe. It covers about 30% of Finland's forest area. Norway spruce is frequently used in research to study many phenomena related specifically to the wood formation and lignification. The principal objective of my thesis work was to reveal an unknown step in the lignification process in developing xylem of Norway spruce, i.e. the initiation site(s) for lignification. To achieve this goal, the aim was to investigate the chemical identity of possible lignification initiation sites in the middle lamellae and cell corners of developing Norway spruce xylem, and to answer the question where in the cell wall soluble monolignols first emerge and lead to the start of lignin formation (polymerization). I was approaching this goal with immunolabeling technique for confocal microscopy and Raman spectroscopy to unravel this initiation site of lignification by using specific monoclonal antibodies for cell wall compounds and comparing the results with the initial lignin deposition sites. To detect the location/distribution of some important polysaccharides and lignin substructure for lignification initiation, monoclonal antibodies i.e. LM10, LM11, LM15, LM24 and antibody Dibenzodioxocin or DBD were applied for confocal microscopy and some monolignol specific spectra were applied for Raman microscopy. The xylan was detected by LM10 in secondary cell wall abundantly and few are in primary cell wall of Norway spruce. The LM11 against arabinoxylan was determined more in primary cell walls but less in secondary cell wall. The location of xyloglucan was identified in the middle lamellae, primary and secondary cell wall of Norway spruce by LM15. The LM24 against glycosylated xyloglucan was found in secondary cell walls, abundantly in cell corners but few in primary cell wall. The primary antibody Dibenzodioxocin or DBD for the lignin substructure revealed that these were present in the mature cells of secondary cell walls (S2 and S3 layers). The lignin substructures DBD were not found in youngest cells where secondary cell walls are absent. The developing xylem of Norway spruce was subjected Raman microscopy and which revealed the locations of cinnamyl alcohol, coniferyl alcohol and coniferyl aldehyde. The cinnamyl alcohol was abundantly found at cell corner and middle lamellae in most developing part of xylem. The coniferyl alcohol was determined only in developing xylem cell corners. The coniferyl aldehyde was observed at cell corners, middle lamella and primary cell walls of developing xylem. The coniferyl aldehyde was located more in mature cells than younger cells. So, the Confocal and Raman microscopy images revealed the possible bindings of monolignols to polysaccharide in young cell corners, cell wall layers and middle lamellae.
  • Peltola, Aino (2021)
    Kurtturuusu (Rosa rugosa) on haitallinen vieraslaji Suomessa. Se on levinnyt alkuperäisiltä esiintymisalueiltaan Koillis-Aasiasta Itämeren ja Pohjanmeren rannikolle sekä Pohjois-Amerikan koillisosiin. Se uhkaa luonnon monimuotoisuutta erityisesti merenrannoilla. Suomessa kaikki hiekkarantojen ja dyynien luontotyypit ovat uhanalaisia ja kurtturuusu vaikuttaa erityisesti niiden ekosysteemeihin muodostamalla suuria tiheitä kasvustoja. Kurtturuusukasvustossa muut lajit vähenevät. Vieraslajilain nojalla kurtturuusun kasvattaminen on kielletty, mutta kasvatuskielto astuu voimaan vasta siirtymäajan jälkeen 1.6.2022. Kurtturuusu on suosittu koristepensas. Siitä on myös jalostettu uusia lajikkeita. Niiden kasvatusta kielto ei koske, koska niiden lisääntymiskyvyn on ajateltu olevan heikko. Tutkimuksen tavoitteena oli selvittää kurtturuusun levinneisyyttä Espoon rannoilla sekä tutkia sen lisääntymiskykyä. Tutkimuksessa kartoitettiin Espoon merenrantoja järjestelmällisesti maastossa havainnoiden ja etsittiin niiltä kurtturuusua. Kasvustojen ominaisuuksia tutkittiin ja selvitettiin morfologisten tuntomerkkien avulla, ovatko ne kurtturuusun perusmuotoa vai jotakin jalostettua lajiketta. Kasvustoista valittiin osa tarkempaa siementutkimusta varten. Siementen elinkykyä tutkittiin tetrazoliumtestin avulla ja kelluntakykyä vesiastioissa. Siementutkimuksessa selvitettiin, eroaako kurtturuusun perusmuodon ja jalostettujen lajikkeiden siementuotto tai siementen elinkyky toisistaan ja kuinka hyvin pähkylät kelluvat. Tilastollisina menetelminä käytettiin varianssianalyysiä ja t-testiä. Kurtturuusua kasvoi Espoon rannoilla runsaasti monenlaisilla kasvupaikoilla sekä istutettuna että villiytyneenä. Mantereella sitä oli enemmän kuin saaristossa. Villiytyneenä tai mahdollisesti villiytyneenä kasvoi vain muutamia kasvustoja jalostettuja kurtturuusulajikkeita. Istutettuina niitä oli enemmän. Kurtturuusun siementuotto vaikuttaa olevan suurempi perusmuodolla kuin jalostetuilla lajikkeilla. Perusmuoto tuotti myös keskimäärin enemmän elinkykyisiä siemeniä. Hajonta molemmissa ryhmissä oli kuitenkin suurta. Osa jalostetuista lajikkeita tuotti melko runsaastikin elinkykyisiä siemeniä, toiset taas hyvin vähän. Kurtturuusun pähkylät kelluivat hyvin. Tulokset tukevat käsitystä siitä, että jalostetut kurtturuusulajikkeet eivät olisi yhtä haitallisia kuin perusmuoto. Sekä perusmuodon että jalostettujen lajikkeiden siementuoton ja elinkyvyn hajonta oli kuitenkin suurta. Eri lajikkeiden eroja olisikin tarpeen selvittää järjestelmällisesti. Kurtturuusulla on hyvät edellytykset levitä veden välityksellä uusille kasvupaikoille, koska se kasvaa rannoilla ja sen siementen kelluntakyky on hyvä. Kurtturuusun kartoitus Espoossa auttaa sen torjunnan suunnittelussa myös muissa kaupungeissa.
  • Vallinkivi, Linda (2022)
    Maisterintutkielman tarkoituksena oli selvittää, mitä talvivihreitä puutarhakasveja Suomessa kasvaa puutarhoissa, ovatko talvivihreät puutarhakasvit ihmisille tärkeitä ja minkälaisia talvivaurioita ihmiset ovat talvivihreillä kasveillaan havainneet. Ilmastonmuutos muuttaa talvet Suomessa vähälumisemmiksi ja pimeämmiksi, ja talvi voi siten tuntua harmaammalta. Talvivihreiden kasvien merkitys ihmisille voi korostua tulevaisuudessa, sillä talvivihreys lisää kasvin koristearvoa ja on erityisen tärkeää pimeänä ja harmaana talvikautena, kun muissa kasveissa ei ole lehtiä. Ilmastonmuutoksen myötä myös talvivihreillä kasveilla havaituissa talvivaurioissa voi tapahtua muutoksia. Tutkimuksen aineisto kerättiin internetissä olleella kyselytutkimuksella. Tietoa kyselystä jaettiin sosiaalisessa mediassa. Kysely kohdennettiin puutarhasta kiinnostuneille ihmisille, ja kysely oli avoinna vastauksille noin kolme viikkoa loka - marraskuussa 2021. Kyselyyn saatiin 154 vastausta eri puolilta Suomea. Vastaukset jaettiin puutarhakasvien kasvuvyöhykkeiden mukaan ja eri kasvuvyöhykkeiden tuloksia verrattiin keskenään. Kyselytutkimuksen tuloksista selvisi, että talvivihreät puutarhakasvit ovat ihmisille tärkeitä, ja erityisesti vähälumisilla alueilla talvivihreät kasvit koetaan todella tärkeiksi. Talvivihreiden kasvien lajimäärä oli tutkimuksessa kaikilla alueilla lähes sama, ja kaikilla alueilla ilmitalvehtijoiden lajimäärä oli suurin muihin kasvien elomuotoihin verrattuna. Tutkimuksen mukaan suosituimpia talvivihreitä puutarhakasveja ovat tuijat, alppiruusut ja maksaruohot. Kaikista talvivaurioista eniten on havaittu lehtien osittaista ruskettumista ja lumen painon aiheuttamia vaurioita. Eniten talvivaurioita on havaittu juuri tuijilla ja alppiruusuilla, joten havaittujen vaurioiden suuri määrä voi liittyä lajien yleisyyteen. Tutkimuksen mukaan kuitenkaan lumen määrä ei vaikuttanut talvivihreillä kasveilla havaittujen talvivaurioiden määrään.
  • Lindholm, Viivi (2022)
    Environmental factors are important tools in constructing methane flux models and estimations. Among the abiotic factors, plants and their functional groups have been noted to have significant effect on methane fluxes for three reasons. First, the vegetation community compositions express their abiotic environmental factors that affect not only the plants, but also local methanogen and methanotroph communities. Second, the vegetation itself might produce methane emissions and have a direct effect on methane balance. Third, the plant functional groups and species have differences in their chemical and physical properties that support different methanogen communities and therefore have an indirect impact on methane fluxes. In this study, methane fluxes of different plant communities were observed during one growing season in northern boreal catchment area in Muonio. Study focuses to determine the link between methane fluxes and abiotic and biotic environmental factors in different vegetation types. Closed chamber technique was used to measure methane and carbon dioxide fluxes from 23 plots every two weeks in period of June-August. Environmental data, such as moisture, temperature species composition etc. were collected from the plots. Vegetation types for each plot were determined via ordination analysis. Linear mixed-effects regression model and generalized additive model were applied and compared to observe the relationships of methane and environmental factors in different vegetation types. Dataset was divided into four vegetation types in clustering analysis: wet fen, pine bog, spruce swamp and forest. The greatest amount (average 5959 µg/m²/h) and biggest range (standard deviation 5285 µg/m²/h) of methane emissions were observed on wettest fen-like study sites. Peatland types in general acted as net methane sources. The driest, forest-like vegetation type acted as a net methane sink. The amount (average -107 µg/m²/h) and range (standard deviation 117 µg/m²/h) of methane fluxes were very moderate in comparison to peatland types. These effects intensified towards the climax of growing season. The most significant environmental factors were mostly abiotic on driest study sites and the whole plant biomass was more significant biotic methane flux regulating factor than plant functional groups. On wetter study sites, the role of abiotic factors decreased, and plant functional group increased. Graminoids were linked to bigger methane emissions especially on wetter study sites. Forest mosses and different shrub types seemed to have a link with lower methane emissions or methane absorption. The effect of other plant functional groups on methane fluxes varied more, and their role remains unclear. None of the environmental factors could estimate the methane flux alone, and the methane budget seems to be a sum of multiple variables in each vegetation type. The role of plant functional groups varied in different vegetation types and was dependent on surrounding vegetation. More research is needed to get better tools to estimate methane balance and to understand the underlying mechanisms in climate and environmental change.
  • Vilhonen, Enni (2021)
    Improving land management to mitigate climate change is important, especially in agriculture on soils with high organic content. Many studies have found evidence that increasing diversity can help to improve plant biomass production and soil carbon storage. This is attributed to complementarity which consists of more efficient resource use due to niche differences and facilitative interactions. For the total climate impact, the effect of greenhouse gas emissions from the soil needs to be considered. To find out if adding more species to a grass mixture could have similar benefits in boreal zone grass cultivation in Finland, an experiment was set up with four different species mixtures, and three levels of species richness were established under a nurse crop. It was additionally of interest if these effects can counter the emissions of cultivation on organic soils. Biomass samples were collected both before the nurse crop was removed and at the end of the growing season. Both species richness and Shannon diversity index were considered as explanatory factors. Carbon exchange, divided into respiration and photosynthetic capacity, as well as nitrous oxide and methane fluxes, were monitored monthly. There was no strong evidence that species richness affects biomass or greenhouse gas fluxes during the first year. The effect of species richness on the biomass was clearer when the diversity index was considered. These results were significant when the lowest biomass values were excluded from the analysis, probably because complementary resource use needs enough biomass to have an effect. The differences in carbon flux measurements may be sensitive to timing within the growing season since the results closest to significant were obtained at the start of the season. At the time, the measurement conditions were good and the nurse crop biomass was small enough not to obscure the effects of grass mixture. When it comes to other greenhouse gases, species richness had most impact on early nitrous oxide emissions, while methane flux probably needs significantly more time for any changes to appear. Overall, the effect of species richness needs to be studied over the full grass cultivation cycle to find out the full effect. Based on current results, increasing species richness may be an option when other methods cannot be used to reduce emissions and improve carbon sink of agriculture.
  • Burg, Skylar (2021)
    In this study, a greenhouse experiment was used to assess if temperature sensitivity, specifically, thermoregulatory plasticity, has a functional role in floral reflectance and pigmentation in a population of P. lanceolata grown in three different temperature treatments, reflecting past, present, and future summer temperatures. Spectrophotometry, surface temperature readings, and near-infrared (NIR) region image analysis were used to identify how the spectral absorbance properties and biochemical makeup of P. lanceolata flowers differed between treatments. Reflectance and phenolic absorbance were both found to be influenced by ambient temperature. However, surface temperature of flower spikes was not affected by growing temperature, reflectance, or phenolic absorbance. The results suggest that Plantago lanceolata may utilize thermoregulatory plasticity in reflectance and phenolic absorbance to adjust to rising temperatures. These findings have important implications in species reactions to climate change and denotes that increased selection on thermal function traits may occur under a future climate scenario of continued warming in temperate and boreal biomes.