Browsing by Subject "ozone"

Stress response in plants is influenced by several external and internal factors and is executed in a modular way. Environmental stimuli or stress is sensed by cellular receptors and the signal is transduced inside cell via the phospho-activation of highly conserved intracellular signaling cascades like mitogen activated protein kinase (MAPK) cascades. The signal then activates biosynthesis pathways of major stress response hormones like Salicylic acid (SA). In Arabidopsis about 90% SA is synthesized via isochorismate pathway and Isochorismate synthase 1 (ICS1) is a rate limiting enzyme in this pathway. In this study, goal was to select transgenic ICS1 (homozygous) candidate lines from parent ICS1-CFP by selective regeneration. Then, by molecular and physiological characterization of transgenic ICS1-CFP plants, the function of ICS1 phosphorylation, more specifically, impact of different photoperiods (Long day; LD and Short day; SD) and stress conditions on ICS1 activity would have resolved. However, there were no homozygous candidate line from any parent ICS1-CFP plants after several screening. Nevertheless, ozone treated stress sensitivity test was performed with heterozygous ICS1-CFP candidate plants (T2 generation). Ozone treated stress depends on stomata factor because ozone enters into plants through stomata. Therefore, stomata index analysis was performed with sid2 and WT (Col-0) phenotypes and grown in LD and SD conditions. Since, stomata number was different between LD and SD plants of both sid2 and WT phenotypes, a different method named Xanthine-Xanthine oxidase (X/XO) treatment was applied that induce oxidative stress regardless of stomata. Although, WT and sid2 had shown sensitivity to the treatment, the overall cell death percentage was very low. Lastly, our aim was to observe the impact of different photoperiods on the activation of two particular MAPKs i.e MPK3 and MPK6 under stress conditions. The phosphorylated (P-MPK3 and P-MPK6) are found abundantly in ozone treated plants as an early response. In this experiment, plants were grown in both LD and SD, stressed with both ozone and X/XO treatments, the activation of P-MPK3 and P-MPK6 was observed by protein level analysis (western blotting) in detailed time course. Although, the activation was visualized in both LD and SD plants, qualitatively the pattern was similar between day type samples and activation signal was very weak in both stress methods. In addition, anti-ICS1 antibody provided by Agrsera TM was tested for its efficiency to detect endogenous ICS1 protein in plants in two experimental set-up. Although the antibody could detect overexpressed ICS1-CFP protein in samples, it was not that efficient to detect endogenous ICS1 in any of the experiments.

In atmospheric sciences, measurements provided by remote-sensing instruments are crucial in observing the state of atmosphere. The associated uncertainties are important in nearly all data analyses. Random uncertainties reported by satellite instruments are typically estimated by inversion algorithms (ex-ante). They can be incomplete due to simplified or incomplete modelling of atmospheric processes used in the retrievals, and thus validating random uncertainties is important. However, such validation of uncertainties (or their estimates from statistical analysis afterwards, i.e. ex-post) is not a trivial task, because atmospheric measurements are obtained from the ever-changing atmosphere. This Thesis aims to explore the structure function method – an important approach in spatial statistics – and apply it to total ozone column measurements provided by the nadir-viewing satellite instrument TROPOMI. This method allows us to simultaneously perform validation of reported ex-ante random uncertainties and to explore of local-scale natural variability of atmospheric parameters. Two-dimensional structure functions of total ozone column have been evaluated based on spatial separations in latitudinal and longitudinal directions over selected months and latitude bands. Our results have indicated that the ex-post random uncertainties estimated agree considerably well with the reported ex-ante random uncertainties, which are within 1-2 DU. Discrepancies between them are very small in general. The morphology of ozone natural variability has also been illustrated: ozone variability is minimal in the tropics throughout the year, whereas in middle latitudes and polar regions they attain maxima in local spring and winter. In every scenario, the ozone structure functions are anisotropic with a stronger variability in the latitudinal direction, except at specific seasons in polar regions where isotropic behaviour is observed. Our analysis has demonstrated that the structure function method is a remarkable and promising tool for validating random uncertainties and exploring natural variability. It has a high potential for applications in other remote sensing measurements and atmospheric model data.