Changes of the Photosynthetic Apparatus in Spirulina Cyanobacterium by Sodium Stress

2000 ◽  
Vol 55 (1-2) ◽  
pp. 16-22 ◽  
Author(s):  
Kavita Verma ◽  
Prasanna Mohanty
Keyword(s):  
Chlorophyll A ◽  
Photosystem I ◽  
Protein Interactions ◽  
Room Temperature ◽  
Photosynthetic Apparatus ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Energy Harvest ◽  
Fluorescence Emission Spectra ◽  
Transfer Processes

Abstract Spirulina platensis trichomes grown in Zarrouks medium having total Na+ concentration as 0.14 ᴍ when transfered to fresh Zarrouks medium containing enhanced level of Na+ ions equal to 0.86 ᴍ showed 30% more accumulation of Na+ intracellularly as compared to the control. An inhibition of photosystem II activity to almost 66% was observed. Also due to this exposure to high Na+, the room temperature absorption characteristics of Spirulina trichomes and the thylakoid membrane preparations w ere altered indicating changes in the chromophore protein interactions and alterations in the phycocyanin/allophycocyanin ratio; there by affecting the energy harvest and energy transfer processes. An increase in the carotenoid absorption was two fold over the control in the treated sample. Similarly, room temperature and low temperature (77 K) fluorescence emission spectra collectively suggested alterations in the chlorophyll a emissions, F 726 of photosystem I reflecting changes in the lipid protein environment of the thylakoid. Our results indicate that in Spirulina the enhanced Na+ level alters the energy harvest and transfer processes. It also affected the emission characteristics of chlorophyll a of photosystem I.

Sustained downregulation of photosystem II in mistletoes during winter depression of photosynthesis

2002 ◽  
Vol 29 (10) ◽  
pp. 1157 ◽  
Author(s):  
Shizue Matsubara ◽  
Adam M. Gilmore ◽  
Marilyn C. Ball ◽  
Jan M. Anderson ◽  
C. Barry Osmond
Keyword(s):  
Excitation Energy ◽  
Excitation Energy Transfer ◽  
Photosynthetic Apparatus ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Thermal Dissipation ◽  
National Academy Of Sciences ◽  
Fluorescence Emission Spectra ◽  
Chl A ◽  
Sun Leaves

Cold acclimation by sustained downregulation of PSII was studied in intact leaves of an Australian mistletoe Amyema miquelii (Lehm. ex Miq.) Tiegh. and its host Eucalyptus. The trends were followed from autumn to spring on leaves that had developed in summer and were exposed to different microclimates with progress of the seasons. In sun leaves of mistletoe, efficiency of excitation energy transfer from light-harvesting pigments to Chl a molecules in PSII core complexes was markedly reduced in winter. Concomitantly, a band in 77K fluorescence emission spectra emerged at 715 nm, in the same way as the cold-hard band found in overwintering snow gum seedlings (Gilmore and Ball 2000, Proceedings of the National Academy of Sciences USA 97, 11 098–11 101). Further, a distinct band, which presumably involves Chl-b-containing antennae complexes, appeared at 705 nm in –2°C fluorescence emission spectra with decreasing intensity of the PSII band. Much shorter PSII fluorescence lifetimes measured in sun leaves of mistletoe that were exhibiting sustained downregulation of PSII indicated enhanced thermal dissipation of excitation energy. Winter acclimation symptoms of the photosynthetic apparatus were more striking in mistletoe sun leaves compared with eucalypt sun leaves. Because the light and temperature environments of sun leaves are similar for the parasite and host, we primarily attribute the enhanced light-acclimation symptoms to the limited photosynthetic capacity of A. miquelii in winter.

scholarly journals The plastome-encoded PsaJ subunit is required for efficient Photosystem I excitation, but not for plastocyanin oxidation in tobacco

2007 ◽  
Vol 403 (2) ◽  
pp. 251-260 ◽  
Author(s):  
Mark A. Schöttler ◽  
Claudia Flügel ◽  
Wolfram Thiele ◽  
Sandra Stegemann ◽  
Ralph Bock
Keyword(s):  
Chlorophyll A ◽  
Photosystem I ◽  
Fluorescence Emission ◽  
Reaction Centre ◽  
Wild Type ◽  
Fluorescence Emission Spectra ◽  
Light Intensities ◽  
In The Wild ◽  
Assimilation Capacity

The functions of several small subunits of the large photosynthetic multiprotein complex PSI (Photosystem I) are not yet understood. To elucidate the function of the small plastome-encoded PsaJ subunit, we have produced knockout mutants by chloroplast transformation in tobacco (Nicotiana tabacum). PsaJ binds two chlorophyll-a molecules and is localized at the periphery of PSI, close to both the Lhca2- and Lhca3-docking sites and the plastocyanin-binding site. Tobacco psaJ-knockout lines do not display a visible phenotype. Despite a 25% reduction in the content of redox-active PSI, neither growth rate nor assimilation capacity are altered in the mutants. In vivo, redox equilibration of plastocyanin and PSI is as efficient as in the wild-type, indicating that PsaJ is not required for fast plastocyanin oxidation. However, PsaJ is involved in PSI excitation: altered 77 K chlorophyll-a fluorescence emission spectra and reduced accumulation of Lhca3 indicate that antenna binding and exciton transfer to the PSI reaction centre are impaired in ΔpsaJ mutants. Under limiting light intensities, growth of ΔpsaJ plants is retarded and the electron-transport chain is far more reduced than in the wild-type, indicating that PSI excitation might limit electron flux at sub-saturating light intensities. In addition to defining in vivo functions of PsaJ, our data may also have implications for the interpretation of the crystal structure of PSI.

Optical Properties and Zinc Nitride Thin Films Prepared Using Magnetron Reactive Sputtering

2014 ◽  
Vol 940 ◽  
pp. 11-15
Author(s):  
Jun Qin Feng ◽  
Jun Fang Chen
Keyword(s):  
Thin Films ◽  
Band Gap ◽  
Near Infrared ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Sem Images ◽  
Fluorescence Emission Spectra ◽  
Glass Substrates ◽  
Zinc Nitride ◽  
Direct Band

Zinc nitride films were deposited by ion sources-assisted magnetron sputtering with the use of Zn target (99.99% purity) on 7059 glass substrates. The films were characterized by XRD, SEM and EDS, the results of which show that the polycrystalline zinc nitride thin film can be grown on the glass substrates, the EDS spectrum confirmed the chemical composition of the films and the SEM images revealed that the zinc nitride thin films have a dense structure. Ultraviolet-visible-near infrared spectrophotometer was used to study the transmittance behaviors of zinc nitride thin films, which calculated the optical band gap by Davis Mott model. The results of the fluorescence emission spectra show the zinc nitride would be a direct band gap semiconductor material.

Stress and Phase Transformation Phenomena in Oxide Films: Real-Time Spectroscopic Measurements

1992 ◽  
Vol 271 ◽  
Author(s):  
Gregory J. Exarhos ◽  
Nancy J. Hess
Keyword(s):  
Phase Transformation ◽  
Applied Pressure ◽  
Oxide Films ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Film Deposition ◽  
Optical Methods ◽  
Fluorescence Emission Spectra ◽  
Line Intensities ◽  
Deposition Parameters

ABSTRACTIn situ optical methods are reviewed for characterization of phase transformation processes and evaluation of residual stress in solution-deposited metastable oxide films. Such low density films most often are deposited as disordered phases making them prone to crystallization and attendant densification when subjected to increased temperature and/or applied pressure. Inherent stress imparted during film deposition and its evolution during the transformation are evaluated from phonon frequency shifts seen in Raman spectra (TiO2) or from changes in the laser-induced fluorescence emission spectra for films containing rare earth (Sm+3:Y3Al5O12) or transition metal (Cr+3 :Al2O3) dopants. The data in combination with measured increases in line intensities intrinsic to the evolving phase are used to follow crystallization processes in thin films. In general, film deposition parameters are found to influence the crystallite ingrowth kinetics and the magnitude of stress and stress relaxation in the film during the transformation. The utility of these methods to probe crystallization phenomena in oxide films will be addressed.

scholarly journals Fluorescence emission spectra of silver and silver/cobalt nanoparticles

2012 ◽  
Vol 19 (3) ◽  
pp. 943-947 ◽  
Author(s):  
Z. Parang ◽  
A. Keshavarz ◽  
S. Farahi ◽  
S.M. Elahi ◽  
M. Ghoranneviss ◽  
...  
Keyword(s):  
Fluorescence Emission ◽  
Emission Spectra ◽  
Cobalt Nanoparticles ◽  
Fluorescence Emission Spectra
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