Ρυθμιστικοί μηχανισμοί της ευαισθησίας / ανθεκτικότητας του φωτοσυνθετικού μηχανισμού στην UVB ακτινοβολία

• Main Author: Sfichi, Liliana
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Crete (UOC) 2006
• Subjects: Φωτοσυνθετικός μηχανισμός; UVB ακτινοβολία; PAR ακτινοβολία; Πολυαμίνες; Φωτοσύστημα ΙΙ; Καροτινοειδή; Photosynthetic apparatus; UVB radiation; PAR; Polyamines; LUCU; PS II; Carotenoids; Scenedesmus obliquus; Φυσικές Επιστήμες; Βιολογία; Natural Sciences; Biological Sciences; Antarctic; Arctic; The Antarctic; Antarc*
• Online Access: http://hdl.handle.net/10442/hedi/16141; https://doi.org/10.12681/eadd/16141

The depletion of stratospheric ozone over the Antarctic and Arctic has been observed since 1974 and 1990, respectively. The principal consequence of stratospheric ozone depletion is the increase in ultraviolet B (UVB: 280-320 nm) radiation reaching the Earth's surface. The potential impact of the enhanced solar UVB radiation predicted by atmospheric models has been the subject of investigation for the last two decades. The data collected from various reports involves roughly 300 species and varieties of plants. Around one-third to one-half of these plants showed physiological damage and/or growth reductions in response to UVB. Many studies have identified PSII as the most labile component of the photosynthetic apparatus to elevated UVB radiation. Still now the underlying mechanisms are a controversial subject that makes difficult to evaluate the environmental relevance of UVB effects on photosynthesis. Several different target sites have been proposed. These include the reaction center of PSII, the light harvesting complex (LHCII) and the acceptor/donor side of PSII. In spite of the great amount of research devoted to the effects of UVB radiation on plants during the past decades, efforts are still needed to clarify the molecular background of the UVB damage, as well as the protective and repair mechanisms. The primary target of UVB radiation in the photosynthetic apparatus is not clearly established. In addition, there are discrepancies between laboratory and field studies that make it difficult to estimate how much the projected increase in UVB radiation at the Earth’s surface will affect photosynthesis. In this context, this work was focused on the factors determining the sensitivity/tolerance of the photosynthetic apparatus to UVB and their regulation. The investigations were carried out in cultures of wt and wt-lhc mutant (similar to wt but without LHCII) of Scenedesmus obliquus. The results demonstrate that there is a fine mechanism that regulates the photosynthetic behavior to UVB radiation. This ...