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- Sjölander, Johan, 1988-
(författare)
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Timing is everything: exploring the role of the circadian clock in plant growth and adaptation
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Due to their sessile nature, plants must precisely time and coordinate their physiological processes with daily and seasonal changes in the environment. In this PhD thesis, I explored the interaction between an internal timekeeper, or circadian clock, and hormonal regulation, and how it may control plant growth and adaptation in the model species Arabidopsis thaliana (Arabidopsis) and hybrid aspen (Populus tremula x P. tremuloides). Our research showed how the circadian clock component ZEITLUPE (ZTL) regulates abscisic acid (ABA)-mediated stomatal closure, indicating its central role in environmental adaptation. We investigated the effects of manipulating gibberellin (GA) metabolism in hybrid aspen by the strategic expression of the Arabidopsis GIBBERELLIN20-OXIDASE1 gene, using a clock-controlled promoter. This approach struck a delicate balance between enhanced growth and seasonal adaptation and showed potential for increased tree performance through biotechnological means.Our studies on the circadian clock components LATE ELONGATED HYPOCOTYL (LHY) and EARLY BIRD (EBI) in hybrid aspen suggested their involvement in regulating GA metabolism and overall plant growth.Taken together, these findings improve our understanding of how plants regulate growth and respond to environmental stresses and help to provide solutions for enhancing plant resilience and productivity.
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| 2. |
- Sjölander, Mattias, 1988-
(författare)
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Blinded by the light : developing models of settlement and mobility with the use of spectroscopy and exploratory methods
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis an exploratory approach has been used to study settlement and mobility among hunter-gatherer societies in Northern Sweden during the 2 000 – 0 BC period. The focus has been on developing the topics of bifacial point use and raw material management of quartzand quartzite materials. The study combines the information generated at multiple analytical scales in order to address knowledge gaps and facilitate new research. The thesis consists of an introductory text and four research papers.The first paper discusses modelling approaches in archaeology. It stresses the interlinked nature of models that are created at different spatial scales, and that weaknesses in lower-lying models may impact higher-level models in a study. The paper also discusses the question of whether an analysis is better suited for modelling in the “variable space”, rather than geographical space, as the data my need to undergo unnecessary simplification that hides certain features.The second paper is an evaluation of the current dating evidence for bifacial points made of quartz or quartzite in Norrland. The study includes 124 radiocarbon datesfrom 30 excavated sites with finds of bifacial points or preforms in the County of Västerbotten. Bayesian modelling is used to evaluate the potential for building a chronological model for bifacial point use in the region. The results indicate that few artefacts can be related to a dated feature, with only 3 dates that may be argued to stem from a secure dating context that dates the points. These dates all fall within the 1 900 – 1 700 BC period.The third paper is a spectroscopic study of quartz and quartzite material. The study is based on a dataset of 126 quartz/quartzite points and preforms from 47 sites along the upper Ångerman River. Non-destructive analysis was performed using three different spectroscopic instrumentations (Near Infrared, Raman, X-Ray Fluorescence). The data were evaluated using Exploratory Data Analysis (EDA). Each instrumentation showed detectable differences in the material, such as the presence or absence of graphite. The study highlights the potential of non-destructive screening methods and lays the foundation for future survey efforts.The fourth paper is a spatial analysis of the distribution of bifacial points and preforms made of quartz and quartzite within the County of Västerbotten. The Ångerman and Ume/Vindel Rivers exhibit different distribution patterns, with higher proportions of preforms closer to the mountains. The distribution pattern is evaluated using Exploratory Data Analysis, including geostatistical methods. The capacity for previous settlement and mobility models to explain the observed patterns are then discussed in the light of factors such as archaeological survey coverage.
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