Phytoplankton Lab Report

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3. GROWTH AND CELL DIVISION OF PHYTOPLANKTON

Phytoplanktons have diversity and are of both the types prokaryotic and eukaryotic. Cell division is the vital process for regeneration. Prokaryotic forms of phytoplankton which comes under domain bacteria divide by basic process of cell division like binary fission. Eukaryotic phytolanktons which comes under domain eukarya are divide by the process of mitosis. For the growth of phytoplankton twenty nutrients are required. Many elements like nitrogen, phosphorous, zinc, magnesium, calcium, silica are required for the growth of phytoplanktons. As these nutrients are present in sea water, phytoplanktons can grow easily. Overexposure to the nutrients to the phytoplanktons can create algal blooms. Algal
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In the past, there had been some speculations that dinoflagellates, which have permanently condensed chromosomes, continuously synthesize DNA throughout the cell cycle (Karentz 1983). Recent evidence, especially from studies using single cell DNA measurements, do not support this hypothesis and indicate a clearly defined S phase (e.g. Bhaud et al. 1991). Interestingly, of all phytoplankton species studied to date, only the dinoflagellate Gyrodinium uncatenum displays a cell cycle with a very long G2 phase (Cetta and Anderson 1990). In order to map more precisely the location of the restriction point within the cell cycle, selective inhibitors may be used: for example hydroxyurea that prevents DNA synthesis and blocks S phase cells, allowing to distinguish between G1 and G2 restriction points (Vaulot et al. 1986).

Temperature appears to have the most uniform action of all factors investigated. When temperature decreases, all phases are lengthened in equal proportions. This suggests that the effect of lowering the temperature on the cell cycle is due to an uniform slowing down of biochemical reactions. Although it has not been studied, temperature stress may have a more specific effect, such as the induction of heat shock proteins (Alexandrov

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