Browsing by Subject "Plant physiology"

Sort by: Order: Results:

Now showing items 1-7 of 7
  • Kemppinen, Jasmin (Helsingin yliopisto, 2020)
    Reactive oxygen species (ROS) are one of the prominent groups of signal compounds that are produced in stress conditions such as excess light. Nuclear protein RADICAL-INDUCED CELL DEAT (RCD1) is sensitive to ROS and controls the expression of organelle components, e.g. mitochondrial alternative oxidases (AOX), thus balancing the redox-status of a plant cell. Plants have fast responses to fluctuating light conditions that happen even before gene expression: i.e. readjusting the capability to receive light energy between the two photosystems by state transitions and increasing the capacity to remove excess energy by non-photochemical quenching (NPQ). Various small auxiliary proteins function in these fast acclimation events. However, many of them are identified on gene level only. The goal of this master’s thesis is to describe the role of a hypothetical protein, PPD8 in Arabidopsis thaliana. We evaluate how PPD8 is associated with RCD1 and a chloroplast thiol-regulator enzyme NTRC. We created double (rcd1 ppd8) and triple mutant plant lines (rcd1 ppd8 ntrc) by crossing single knockout lines ppd8, rcd1 and ntrc. Photosynthetic performance, NPQ and sensitivity to ROS were observed in each line by using two different chlorophyll fluorescence measurement methods: pulse-amplitude-modulation (PAM) and novel OJIP imaging fluorometry. The leaves were exposed to methyl viologen (MV), which accelerates the chloroplastic ROS production in light, and also to hypoxic conditions in order to study how the effect of MV is altered in low concentrations of oxygen. Additionally, we examined the amount of photosynthetic proteins and stoichiometry of photosystems in ppd8, rcd1 and rcd1 ppd8 by immunological methods. Finally, PPD8 gene with attached hemagglutinin encoding tags was generated by cloning and reintroduced back to the ppd8 knockout lines. Plants lacking RCD1 are very tolerant against MV and ROS, but when rcd1 was crossed with ppd8 the resistance was suppressed. Both rcd1 ppd8 and ppd8 exhibited elevated chlorophyll fluorescence and NPQ values. The removal of PPD8 gene had an impact on the abundance and the stoichiometry of photosynthetic proteins reducing the plants’ performance. When RCD1, PPD8 and NTRC were simultaneously absent the plants had major defects: their NPQ and fluorescence values were drastically increased. Furthermore, several results hinted towards possible issues in the function of ATP synthase in ppd8 background plants. It is also known that NTRC regulates ATP synthase: taken together, the results suggest that PPD8 is necessary for a fully operative ATP synthase and photosynthetic machinery. By reintroducing PPD8 to knockout line ppd8, the phenotype could be reverted back to wild type -like, thus confirming the significance of the PPD8 gene product in plant.
  • Halabi, Sanna (University of Helsinki, 2000)
  • Wang, Di; Puttonen, Eetu; Casella, Eric (Elsevier BV, 2022)
    International Journal of Applied Earth Observation and Geoinformation
    The mechanisms involved in organ motions are central to our understanding of how plants develop and respond to environmental stimuli such as light quality, gravity, and water availability throughout time. Recent studies have shown that motions in plants such as circadian rhythms and growth patterns, can be recorded and quantified from time series of terrestrial laser scans (TLS). However, most works monitored the changes of certain functional traits such as height and volume to detect and analyze structural dynamics. A generic method for retrieving fine-scale three-dimensional (3D) motion fields of plant structural movements is still missing. We present PlantMove, a new fully automatic tool to quantify 3D motion fields of plant structural movements with varied magnitudes using TLS point clouds acquired over different time periods. The method uses spatio-temporal point cloud registration embedded in a progressive and coarse-to-fine framework, enabling an efficient processing of large datasets with complex structures. PlantMove was first demonstrated on synthetic plant datasets, displaying millimeter to centimeter level accuracy of retrieved motion fields. In addition, PlantMove was used to assess circadian rhythms on a birch tree from TLS data acquired over the course of one night with about one-hour time intervals, and growth patterns on an English oak from a four-year TLS survey. PlantMove can help to better monitor plant phenotypic plasticity with fine level of details, and can contribute to improve our understanding in plant dynamics across various spatial and temporal scales.