Stress is ubiquitous for all organisms, however, impacts vary depending on type and strength of the stressor, as well as the organism’s tolerance. Currently, ionizing radiation is described by the “linear no threshold” model. However, considerable research suggests that a hormetic or threshold model may better describe radiation exposure. Using male house crickets the impacts of early-life radiation on life history and reproductive traits, molecular biomarkers, and trans-generational impacts were analyzed. Generally, radiation impacts were best described by non-linear modelling. Multiple aspects of sexual signalling were disrupted by radiation, and impacts emerged in F1 offspring through extended longevity and superior survivorship. / Thesis / Master of Science (MSc)

Die vorliegende Arbeit befasst sich mit der Charakterisierung der Strahlungsstresstoleranz am Beispiel von Impatiens Genotypen unter Berücksichtigung morphologischer, anatomischer und physiologischer Merkmale. Von 2012 bis 2014 wurden Pflanzen von fünf Impatiens Genotypen bei unterschiedlichem Strahlungsangebot im Gewächshaus kultiviert. Zur Sensibilisierung des Pflanzenmaterials wurde ein Teil der Pflanzen während der Anzucht mit einer herkömmlichen Schattierung stark schattiert (70 % Lichtminderung). Nach 10 Wochen bei unterschiedlichem Strahlungsangebot wurden Blattproben für histologische Untersuchungen entnommen und fünf Pflanzen je Genotyp für Strahlungsstressapplikationen in Pflanzgefäße verpflanzt. Diese Applikationen erfolgten im Freiland unter einem UV-undurchlässigen und einem UV-durchlässigen Foliendach, sowie unter voller Sonne mit und ohne Bewässerung. Während der Stressapplikation wurde die stomatäre Leitfähigkeit und die Chlorophyll-Fluoreszenz gemessen, Thermalbilder erstellt und die Nekrosenintensität täglich dokumentiert. Innerhalb von sieben Tagen waren an schattiert angezogene Pflanzen, im Gegensatz zu unschattiert angezogenen Pflanzen, deutliche Reaktionen an sonnenexponierten Blättern in Form von Nekrosen zu erkennen. Ein zusätzlicher Einfluss von Trockenstress intensivierte diese Reaktion nicht. Zudem wurde deutlich, dass physiologische Messungen während der Stressapplikation nicht mit dem Auftreten der Nekrosen übereinstimmten. Hingegen zeigten Blattquerschnitte und physiologische Messungen nach der Anzucht, dass Blätter, die sich unter hohem Strahlungsangebot entwickelt haben, ein dickeres Palisadenparenchym, mehr Chloroplasten und eine höhere Sättigungskurve der Photosyntheserate aufweisen. Letztendlich zeigt die vorliegende Arbeit, dass die Strahlungsstresstoleranz der Pflanzen stärker von den Anzuchtbedingungen beeinflusst wird, als vom Genotyp, was die Identifikation einer Strahlungsstresstoleranz erschwert. / The aims of the investigation were to characterize the light stress reaction regarding the morphology, anatomy and physiology of five Impatiens varieties. For the trials from 2012 to 2014, plants of each variety were grown in greenhouses at different light conditions. To produce plants with a higher light sensitivity, the light intensity was reduced by using common shading systems (70 % shading). After 10 weeks of pre-treatment at different light conditions, five plants of each variety were transferred into balcony boxes. To determine the anatomical reactions, some leaves were harvested and used for histological investigations. For the light stress treatment, plants were placed outside under UV-impermeable foil, UV-permeable foil and in full sun radiation with and without irrigation. In addition, the stress reaction of plants was evaluated by measuring the stomatal conductance and chlorophyll fluorescence, by using thermal images and by documenting leaf damage daily. Within seven days of light stress the plants subjected to the low light pre-treatment had a significantly higher stress reaction on sun exposed leaves than the plants subjected to the high light pre-treatment. The additional drought stress did not intensify this reaction. Furthermore, the physiological measurements during the stress application were not confirmed by the emergence of leaf damage. But pictures of tissue sections and physiological measurements after pre-treatment illustrated that the leaves developed under high light conditions have more densely packed palisade parenchyma, more chloroplasts and a greater saturation curve of photosynthesis rate compared to the leaves developed in low light conditions. Finally, the results demonstrated that the conditions of plant cultivation influence the light stress adaption stronger than the genotype what makes the identification of light stress tolerant difficult.

No description available.

The variability of the nearshore wave climate is investigated via the analysis of over 10 years of Acoustic Doppler Current Profiler (ADCP) data from a gauge deployed at Melbourne Beach, FL. Examples of large yearly variability in the significant wave height, peak period, mean direction and energy distribution are found in the data. Estimates of the averaged spectra for the entire record show that the average wave energy is distributed almost symmetrically with the peak being close to shore-normal. It was expected that the peak would be shifted towards the north of shore-normal considering net north to south longshore sediment transport at this location. Further analysis of the directional spectra partitioned into three directional windows reveals that waves from the southeast (avg. Hmo = 0.78 m) are less energetic than those from the northeast (avg. Hmo = 0.87 m), but they arrive from the south 53% more often. Additionally, energy-based significant wave height (Hmo), peak period (Tp) and mean period (Tmean) distributions are studied and modeled with notable success. Radiation stress (Sxy) estimates are computed using both rigorous integration as well as parameter-based approximations. These two estimates are correlated but the parameter-based approximation over predicts Sxy by 42%, because this method assigns all the wave energy into one direction (Ruessink et al., 2001). Finally, it is shown by the Sxy total average that the net longshore forcing at this location is indeed north to south, but yearly and seasonal variability were quite high. The results indicate that short-term wave records may not provide accurate information for planning purposes. For example, if only 3 months of data were collected at this site, there would be a 33% chance that the mean longshore forcing would be erroneously directed from south to north.