scholarly journals Ultraviolet-B Radiation Impacts Light-Mediated Turnover of the Photosystem II Reaction Center Heterodimer in Arabidopsis Mutants Altered in Phenolic Metabolism

2000 ◽  
Vol 124 (3) ◽  
pp. 1275-1284 ◽  
Author(s):  
Isabelle S. Booij-James ◽  
Shyam K. Dube ◽  
Marcel A.K. Jansen ◽  
Marvin Edelman ◽  
Autar K. Mattoo
Keyword(s):  
Photosystem Ii ◽  
Reaction Center ◽  
Ultraviolet B ◽  
Phenolic Metabolism ◽  
Arabidopsis Mutants ◽  
Ultraviolet B Radiation

Effects of Ultraviolet-B Radiation on Photosystem II of the Cyanobacterium Synechocystis sp. PCC 6083

1996 ◽  
Vol 242 (3) ◽  
pp. 799-806 ◽  
Author(s):  
Giorgio Mario Giacometti ◽  
Roberto Barbato ◽  
Simona Chiaramonte ◽  
Giulia Friso ◽  
Fernanda Rigoni
Keyword(s):  
Photosystem Ii ◽  
Ultraviolet B ◽  
Ultraviolet B Radiation ◽  
Synechocystis Sp

Ultraviolet-B Radiation Induced Damage to the Function and Structure of Photosystem II

1995 ◽  
pp. 3425-3428
Author(s):  
Imre Vass ◽  
László Sass ◽  
Cornelia Spetea ◽  
Éva Hideg ◽  
Vasili Petrouleas
Keyword(s):  
Photosystem Ii ◽  
Ultraviolet B ◽  
Ultraviolet B Radiation ◽  
Radiation Induced

Leaf Hairs of Olive (Olea europaea) Prevent Stomatal Closure by Ultraviolet-B Radiation

1994 ◽  
Vol 21 (3) ◽  
pp. 293 ◽  
Author(s):  
G Grammatikopoulos ◽  
G Karabourniotis ◽  
A Kyparissis ◽  
Y Petropoulou ◽  
Y Manetas
Keyword(s):  
Photosystem Ii ◽  
Water Vapour ◽  
Photosynthetic Rate ◽  
White Light ◽  
Photochemical Efficiency ◽  
Ultraviolet B ◽  
Hair Removal ◽  
Leaf Hairs ◽  
Ultraviolet B Radiation ◽  
Leaf Resistance

In olive (Olea europaea L.), hair removal had no effect on the photosynthetic rate and the apparent leaf resistance to water vapour diffusion in leaves illuminated with white light (900 μmol m-2 s-1 photosynthetically active radiation) devoid of ultraviolet-B radiation. In addition, intact and dehaired leaves showed no significant differences in absorptance in the visible spectral region, while leaf temper- ature was independent of hair removal. These results indicate that leaf hairs of O. europaea may play only a marginal role in leaf energy balance and transpiration. When the white light was supplemented with ultraviolet-B radiation (5.89 W m-2), however, there was a considerable decrease in the photo- synthetic rate, and a simultaneous increase in leaf resistance to water vapour in dehaired leaves. Photochemical efficiency of photosystem II, evaluated from chlorophyll fluorescence emitted from the illuminated side, was reduced in all cases, but the reduction in dehaired, ultraviolet-B treated leaves was more pronounced and irreversible, indicating that the reduction of the photosynthetic rate may result from both stomatal limitation and electron flow inhibition. Photosynthetic capacity of dehaired leaves, measured at 5% CO2, however, was not influenced by ultraviolet-B radiation. We suggest, therefore, that ultraviolet-B radiation reduces photosynthetic rates by closing the stomata, while the observed reduction in photosystem II photochemical efficiency may concern only a superficial chloroplast population, contributing negligibly to whole leaf photosynthesis. Under the conditions of our experi- ments, the protective function of the indumentum against ultraviolet-B radiation predominates over the water conservation function.

Ultraviolet-B Induced Damage to Photosystem II in Intact Filaments of Spirulina platensis

1998 ◽  
Vol 53 (5-6) ◽  
pp. 369-377 ◽  
Author(s):  
Bala Krishna Kolli ◽  
Swati Tiwari ◽  
Prasanna Mohanty
Keyword(s):  
Energy Transfer ◽  
Photosystem Ii ◽  
Chlorophyll A ◽  
Spirulina Platensis ◽  
Pool Size ◽  
Ultraviolet B ◽  
Emission Characteristics ◽  
Reaction Centre ◽  
Small Shift ◽  
Ultraviolet B Radiation

Abstract When Spirulina platensis filaments were exposed to 0.75 mW.m-2.s-1 of ultraviolet-B radiation (the ultraviolet-B radiation under clear sky condition is ~1.0 mW.m-2.s-1), an inhibition in photosystem II activity was observed, the inhibition being 90% after 90 min exposure. Upon exposure to ultraviolet-B, the room temperature emission characteristics of Spirulina cells were altered when excited with light primarily absorbed by chlorophyll a or phycobilisomes. When the cells were exposed for 3 h the emission at 685 nm (F685), when excited at 440 nm (primarily chlorophyll a absorption), was enhanced compared to 715 nm (F 715) band of photosystem I suggesting a decrease in energy transfer from photosystem II to photosys­ tem I. Similarly, when the cells were excited at 580 nm (primarily the phycobilisomes), the ratio of emission intensity at 685 nm (F685) to that of 655 nm (F655) was decreased in the exposed cells. This change in emission characteristics seems to be linked with the uncoupling of the energy transfer from allophycocyanin to chlorophyll a of photosystem II. A small shift in emission peak positions was also indicated when excited either at 440 nm or 580 nm. Analysis of the fast induction of chlorophyll a transients in the presence and absence of 10 μm 3-(3,4-dichlorophenyl)-l,l-dimethylurea (DCMU) indicated that ultraviolet-B expo­ sure initially affects Qᴀ, the primary stable acceptor of photosystem II, and then the plastoquinone (PQ) pool. Our results on the loss in photosystem Il-catalyzed Hill activity with p-benzoquinone or dichlorobenzoquinone as electron acceptors also supports the contention that ultraviolet-B, even at low dose, initially alters the Qᴀ of photosystem II and subsequently PQ pool. The analysis of functional pool size of Spirulina suggests a substantial decrease in the functional pool size after 2 h UV-B exposure. These results indicate that in Spirulina low intensity of ultraviolet-B initially damages the reaction centre of photosystem II.

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