Inhibition of photosynthesis by ultraviolet radiation as a function of dose and dosage rate: Results for a marine diatom

1991 ◽  
Vol 111 (2) ◽  
pp. 183-190 ◽  
Author(s):  
J. J. Cullen ◽  
M. P. Lesser
Keyword(s):  
Ultraviolet Radiation ◽  
Marine Diatom ◽  
Dosage Rate

Ultraviolet radiation stimulated activity of extracellular carbonic anhydrase in the marine diatom Skeletonema costatum

2009 ◽  
Vol 36 (2) ◽  
pp. 137 ◽  
Author(s):  
Hongyan Wu ◽  
Kunshan Gao
Keyword(s):  
Carbonic Anhydrase ◽  
Ultraviolet Radiation ◽  
Uv Radiation ◽  
Carbon Fixation ◽  
Skeletonema Costatum ◽  
Marine Phytoplankton ◽  
Marine Diatom ◽  
Redox Activity ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon

Previous studies have shown that reduced levels of solar UV radiation (280–400 nm) can enhance photosynthetic carbon fixation of marine phytoplankton, but the mechanisms are not known. The supply of CO2 for photosynthesis is facilitated by extracellular (periplasmic) carbonic anhydrase (CAe) in most marine phytoplankton species. The present study showed that the CAe activity of Skeletonema costatum (Greville) Cleve was stimulated when treated with UV-A (320–395 nm) or UV-A + UV-B (295–320 nm) in addition to visible radiation. The presence of UV-A and UV-B enhanced the activity by 28% and 24%, respectively, at a low irradiance (PAR 161, UV-A 28, UV-B 0.9 W m−2) and by 21% and 19%, respectively, at a high irradiance (PAR 328, UV-A 58, UV-B 1.9 W m−2) level after exposure for 1 h. Ultraviolet radiation stimulated CAe activity contributed up to 6% of the photosynthetic carbon fixation as a result of the enhanced supply of CO2, as revealed using the CAe inhibitor (acetazolamide). As a result, there was less inhibition of photosynthetic carbon fixation compared with the apparent quantum yield of PSII. The UV radiation stimulated CAe activity coincided with the enhanced redox activity at the plasma membrane in the presence of UV-A and/or UV-B. The present study showed that UV radiation can enhance CAe activity, which plays an important role in counteracting UV inhibition of photosynthesis.

scholarly journals Photoacclimation modulates excessive photosynthetically active and ultraviolet radiation effects in a temperate and an Antarctic marine diatom

2006 ◽  
Vol 51 (3) ◽  
pp. 1239-1248 ◽  
Author(s):  
Willem H. van de Poll ◽  
Anne-Carlijn Alderkamp ◽  
Paul J. Janknegt ◽  
Jan Roggeveld ◽  
Anita G. J. Buma
Keyword(s):  
Ultraviolet Radiation ◽  
Radiation Effects ◽  
Marine Diatom ◽  
Antarctic Marine

Applications of Photoelectron Microscopy

1976 ◽  
Vol 34 ◽  
pp. 506-507
Author(s):  
William J. Baxter
Keyword(s):  
Electron Microscopy ◽  
Thermal Decomposition ◽  
Chemical Composition ◽  
Ultraviolet Radiation ◽  
Thin Layer ◽  
Edge Effects ◽  
Electron Optics ◽  
Surface Layers ◽  
Crystalline Orientation ◽  
Fluorescent Screen

In this form of electron microscopy, photoelectrons emitted from a metal by ultraviolet radiation are accelerated and imaged onto a fluorescent screen by conventional electron optics. image contrast is determined by spatial variations in the intensity of the photoemission. The dominant source of contrast is due to changes in the photoelectric work function, between surfaces of different crystalline orientation, or different chemical composition. Topographical variations produce a relatively weak contrast due to shadowing and edge effects.Since the photoelectrons originate from the surface layers (e.g. ∼5-10 nm for metals), photoelectron microscopy is surface sensitive. Thus to see the microstructure of a metal the thin layer (∼3 nm) of surface oxide must be removed, either by ion bombardment or by thermal decomposition in the vacuum of the microscope.

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