جستجوی مقالات مرتبط با کلیدواژه "دونالیه لا" در نشریات گروه "زیست شناسی"

Unicellular green alga Dunaliella has capability to accumulate massive beta-carotene in its chloroplasts under unsuitable conditions. In this study D.bardawil and D.salina were cultured on mediums containing 1M, 2M and 3M of NaCl at 25°C in six replicate. After two weeks, when beta-carotene content was increased, samples were transferred to 0°C and after 8h they were returned to 25°C. Then parameters of Chl-a fluorescence was measured and its parameters were evaluated. According to the result, amount of beta-carotene in D. bardawil especially in 3M NaCl was higher than D. salina. In addition, analysis of fluorescence parameters such as FV/Fo (activity of the water-splitting complex), φPo (electron transport to pheophytin and QA), ψo (electron transport from QA to QB), φEo (electron transport in electron transport chain), φRo (reduction rate of end acceptor of electron transport chain) and φDo (rate of energy dissipation) indicated less changes in D. bardawil than D. salina in 3M NaCl when return to 25°C. According to the result, it seems that in the medium containing high concentration of NaCl, D. bardawil has better recovery when transferred from 0°C to 25°C. In such condition, D. bardawil is able to accumulate more beta-carotene than D. salina and in turn is able to protect PSII reaction centers.

the aim of this study was to investigate the effect of iron on cell division، interacellular beta-carotene and chlorophyll synthesis in unicellular green alga Dunaliella. In this study 4، 32، 64، 128، 256 and 512µM concentrations of iron was applied on D. bardawil and D. salina. The culture media were kept in a growth chamber in a light/ dark regime of 16/8 hours at 26±2 °C. Then beta-carotene، chlorophyll content and cell divisions were determined. In both species the maximum cell growth was observed in 4 µM and the amount of chlorophyll as well as cell growth decreased by the increase of iron concentration in the medium. The maximum reduction of the chlorophyll and cell growth was observed in 512 µM، where as the maximum intracellular beta-carotene content was shown in 128 µM. Results showed that probably free radicals contents of both species have been increased in presence of iron. Iron treatment decreased the chlorophyll content to reduce the free radicals produced due to excitation of chlorophyll molecules. Moreover، the cells produced high amount of beta-carotene as an antioxidant against free radicals in presence of Iron. It seems D. salina has better performance in presence of high concentration of iron than D. bardawil due to less synthesis of beta-carotene and more production of other antioxidants as well as reduction of chlorophyll production.

The first location of cold stress effect on PSII in plants and algae is not fully clear. Therefore, the effect of low temperature (8°C) on the activity of different parts of PSII were investigated in D. salina as plant model system is investigated using chlorophyll a fluorescence kinetics. In this study unicellular green alga, D. salina, 200 UTEX strain was used. The Algae were cultured in the medium containing 1M of NaCl at 8°C or 25°C in triplicates. Then the parameters of Chl-a fluorescence was measured in various interval after cold stress. The results showed that at temperatures 8°C, the rate of parameters FV/Fo, φPo, ψo, φEo, φRo and PIABS in the species D.salina were decreased in comparison with the control (25°C). Whereas, the rate of parameters φDo and ABS/RC were decreased. According to the results, decreasing of efficiency of water-splitting complex under low temperature stress probably has a significant effect on electron transport to the PSII electrons acceptors and creates imbalance in activity of PSII electron transport chain. The effect of cold stress on water-splitting complex, in turn, seems to decrease the rate of electron transport to Pheophytin and QA and from QA to QB, plastoquinone pool and finally reduction of end acceptor at photosystem I electron acceptor side. It could be finalized that the water-splitting complex is the first site that is affected by cold stress in PSII of D.salina cells.