碩士 / 國立清華大學 / 生物資訊與結構生物研究所 / 93 / PartI
The growth period for many macroalgae in Ken Ting is from March to June. According to preview studies, Codium edule has the largest covering ratio on the coral reef among all the macroalgae, but its population above 5m depth of subtidal drastically decreases from July to September. After November C. edule gradually recover and rapid growth state until March next year. In this article, we use the chlorophyll fluorescence and transmission electrons microscopic（TEM） to find out the possible reasons for C. edule drastically decrease between July to September.
According to chlorophyll fluorescence studies, we found that C. edule lost photosynthetic circadian rhythm at 33℃, but it was not lethal at the temperature. Upon exposure to 35℃, the photosynthetic activity of the algae would drastically decrease after 4 hours and drop to zero after 8 hours. From TEM studies, the vacuoles reduce in size which was accompanied by the appearance of many small vesicles after exposing to 35℃ about 4 hours. In the meantime, the algae became soft and underwent plasmolysis that is believed a key induced cell death. Finally, the vacuole collapsed completely and the plasmamembrane destroyed which means the algal cells started to necroses.
In summery, our data suggested that 35℃ would cause the vacuole to collapse and lead to C. edule is cell death. This might be for the reason it drastically decrease between July to September.
PartII
In this study, we examined the programmed cell death （PCD）of synchronous Chlorella pyrenoidosa culture by transmission electron microscopic（TEM）. The PCD started right affect high temperature stress（46.5℃）followed by continuous illumination under normal culture condition.
We noticed that high temperature stress induced chromatin condensation around the inner membrane of nuclear and something in vacuole. These phenomena elucidated the immediate effect on Chlorella brought about by heat stress. In 6 h after stress we found that Chlorella cell were bleached. But according to the images of TEM, the destruction of the thylakoids started at 8 h but not at 6 h. The direction of thylakoid destruction was from inner to outer side of Chlorella cells. At the same time, the structures of vacuole, mitochondria and nuclei in Chlorella also disappeared. These showed that there were dramatic morphological changes in Chlorella between 6-8h. The disappearances of organells were followed by and then the cytosolic condensation which in turn induced plasmolysis, but the later phenomenon would vanished gradually. In addition, the chromatins condensation formed an annular structure that was preserved for more than two days.
In summery, Chlorella would die after heat treatment. The death was induced by a spontaneous mechanism and a programmed process different from ordinary.
| Identifer | oai:union.ndltd.org:TW/093NTHU5112016 |
| Date | January 2005 |
| Creators | 李讚虔 |
| Contributors | 徐邦達 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 110 |
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