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2. Changes in CO2 exchange rate, stomatal conductance, activities of photosystems 1 and 2, and chloroplast polypeptide profile induced by simulated acidic rain
- Creator:
- Kumaravelu, G. and Ramanujam, M. P.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- absorption spectra, chlorophyll fluorescence, photosynthesis, and Vigna radiata
- Language:
- Multiple languages
- Description:
- In seedlings of Vigna radiata (L.) R. Wilczek cultivars ADT-1 and CO-5 exposed to acidic showers (H2SO4 : HNO3 : HCl, 4 : 2 : 1, v/v) of different pH (7.0, 5.5, 4.0, and 2.5) for 10 d, net CO2 uptake and stomatal conductance were reduced. The chlorophyll (Chl) a and b contents were reduced but the carotenoid (Car) content increased. In vivo Chl a fluorescence patterns of both the cultivars were altered. No significant change in photosystem (PS) 1 activity was observed except at pH 2.5 where an inhibition was evident. By contrast, PS2 activities declined rapidly with increasing acidity. The room temperature absorption spectra of isolated chloroplasts showed very little changes. SDS-PAGE analysis revealed depletion of 23, 33, and 55 kDa polypeptides. Cultivar CO-5 was more sensitive to acidic rain than cv. ADT-1. and G. Kumaravelu, M. P. Ramanujam.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3. Effect of high temperature on photosynthetic electron transport activities of the cyanobacterium Spirulina platensis
- Creator:
- Venkataramanaiah, V., Sudhir, P., and Murthy, S. D. S.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- absorption spectra, energy transfer, fluorescence emission spectra, and photosystems 1 and 2
- Language:
- Multiple languages
- Description:
- The activities of photosystem 2 (PS2) and whole chain electron transport declined in high temperature treated cells at the room temperature beyond 35 °C, while photosystem 1 (PS1) showed increased activity. Thylakoid membrane studies did not exhibit increase in PS1 activity indicating that the enhancement of PS1 activity is due to permeability change of cell membranes. However, the electron transport activity measured from reduced duroquinone to methylviologen which involves intersystem electron transport was extremely sensitive to high temperature. The activity of PS2 at different irradiance, which was accompanied by alterations in absorption and fluorescence emission properties, indicated changes in the energy transfer processes within phycobilisomes. Thus high temperature has multiple target sites in photosynthetic electron transport system of Spirulina platensis. and V. Venkataramanaiah, P. Sudhir, S. D. S. Murthy.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
4. Excitation energy transfer in cyanobacteria Synechocystis embedded in polymer film and partially bleached by polarized irradiation
- Creator:
- Goc, J., Klecha, K., Waszkowiak, A., Miyake, J., and Frąckowiak, D.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- absorption spectra, fluorescence spectra, photoacoustic spectra, phycobilisomes, and polarized radiation spectroscopy
- Language:
- Multiple languages
- Description:
- The polarized absorption, photoacoustic, fluorescence emission, and fluorescence excitation spectra of whole cells of cyanobacteria Synechocystis sp. embedded in a polymer film were measured. The bacteria cells, as it follows from anisotropy of absorption and fluorescence spectra, were even in a non-stretched polyvinyl alcohol film oriented to a certain extent. The measurements were done for such film in order to avoid the deformation of cyanobacteria shapes. Part of the samples was bleached by irradiation with strong polarized radiation with electric vector parallel to the orientation axis of cells. The anisotropy of photoacoustic spectra was higher than that of absorption spectra and it was stronger changed by the irradiation. Polarized fluorescence was excited in four wavelength regions characterised by different contribution to absorption from various bacteria pigments. The shapes of emission spectra were different depending on wavelength of excitation, polarization of radiation, and previous irradiation of the sample. The fluorescence spectra were analysed on Gaussian components belonging to various forms of pigments from photosystems (PS) 1 and 2. The results inform about excitation energy transfer between pools of pigments, differently oriented in the cells. Energy of photons absorbed by phycobilisomes was transferred predominantly to the chlorophyll of PS2, whereas photons absorbed by carotenoids to chlorophylls of PS1. and J. Goc ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
5. High temperature induced alterations in energy transfer in phycobilisomes of the cyanobacterium Spirulina platensis
- Creator:
- Murthy, S. D. S., Ramanaiah, V. V., and Sudhir, P.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- absorption spectra and fluorescence emisson spectra at room and low temperature
- Language:
- Multiple languages
- Description:
- Exposure of intact cells of Spirulina to high temperature (HT) stress (40-60 °C) caused decrease in absorption spectrum and fluorescence emission spectrum. Low temperature emission spectra were altered at phycocyanin (PC) level. Room and low temperature emission spectra of intact phycobilisomes showed that PC was the main target in this cyanobacterium for the altered energy transfer under HT. and S .D. S. Murthy, V. V. Ramanaiah, P. Sudhir.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
6. Interactions of chlorophyll and polypeptide mixture with bacterial reaction centres
- Creator:
- Enomoto, H., Takeda, S., Nakamura, C., Miyake , J., Ptak, A., Dudkowiak, A., and Frąckowiak, D.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- absorption spectra, fluorescence spectra, photoacoustic spectra, Rhodobacter sphaeroides, and thermal deactivation
- Language:
- Multiple languages
- Description:
- In aqueous solutions of chlorophyll (Chl) a with synthesized polypeptides, at high ratios of Chl to polypeptides (about 75-150 µM to 500 µM) clusters of polypeptides and pigment molecules were formed. The main absorption maxima of more than one formed cluster were located at about 500 nm (Soret band) and in the region of 720-806 nm (red band). The formation of these clusters was fairly slow (some hours) at room temperature and even slower at 4 °C. The rate of cluster formation increased with the increase in Chl concentration. The addition of the even low amount of reaction centres (RCs), separated from the purple bacteria Rhodobacter sphaeroides, to the sample of Chl with polypeptides caused a very strong decrease in the efficiency of cluster formation, and a change in concentration ratios of various pigment-polypeptide aggregates. It was probably a competition between the interaction of Chl with polypeptides and with the RCs. The yield of thermal deactivation of the clusters was high, much higher than that for the RCs alone and it was different for various types of cluster. The clusters absorbing at 725-750 nm were fluorescent with maximum of emission at about 770 nm, whereas clusters absorbing at about 800 nm were nonfluorescent. and H. Enomoto ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7. Regulation mechanism of excitation energy transfer in phycobilisome-thylakoid membrane complexes
- Creator:
- Li, Ye, Zhang, Jianping, Zhao, Jingquan, and Jiang, Lijing
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- absorption spectra, allophycocyanin, betaine, DCMU, fluorescence spectra, models of energy transfer, N-ethylmaleimide, photosystems 1 and 2, and state transition
- Language:
- Multiple languages
- Description:
- Regulation mechanism of excitation energy transfer between phycobilisomes (PBS) and the photosynthetic reaction centres was studied by the state transition techniques in PBS-thylakoid membrane complexes. DCMU, betaine, and N-ethylmaleimide were applied to search for the details of energy transfer properties based on the steady fluorescence measurement and individual deconvolution spectra at state 2 or state 1. The closure of photosystem (PS) 2 did not influence on fluorescence yields of PS1, i.e., energy could not spill to PS1 from PS2. When the energy transfer pathway from PBS to PS1 was disturbed, the relative fluorescence yield of PS2 was almost the same as that of PS2 in complexes without treatment. If PBSs were fixed by betaine, the state transition process was restrained. Hence PBS may detach from PS2 and become associated to PS1 at state 2. Our results contradict the proposed "spill-over" or "PBS detachment" models and support the mobile "PBS model". and Ye Li ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
8. The salinity tolerance of freshwater cyanobacterium Synechococcus sp. PCC 7942 is determined by Its ability for osmotic adjustment and presence of osmolyte sucrose
- Creator:
- Ladas, N. P. and Papageorgiou, G. C.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- absorption spectra, cell doubling, chlorophyll content and fluorescence, cytoplasmic osmolality, glucose, NaCl, saccharose, and sugars
- Language:
- Multiple languages
- Description:
- We investigated the factors that impose an upper limit of salinity tolerance to the unicellular freshwater cyanobacterium Synechococcus sp. PCC 7942. Above approx. 0.4 M NaCl, Synechococcus cells cease to proliferate, after having accumulated 0.3 M sucrose. Cells that pre-accumulated sucrose could tolerate up to 0.5 M NaCl, but not 0.6 M NaCl. After exposure to 0.5 M NaCl or higher, the cells were irreversibly modified becoming unable for osmotic volume adjustments. and N. P. Ladas, G. C. Papageorgiou.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public