Effect of light state transitions on the apparent absorption cross section of Photosystem II in Chlorella
The distribution of excitation energy between photosystems may profoundly affect the quantum yield of photosynthetic oxygen evolution. Excitation energy absorbed by pigment molecules is transferred to reaction centers, where it may potentially drive a photochemical event. To balance the photochemical events in PSII with those in PSI, excitation energy may be transferred between PSII and PSI. This type of energy transfer has been inferred primarily in the steady state quantum yield of oxygen evolution and/or fluorescence with changes in excitation wavelength. These so called ''state transitions'' have been attributed to changes in either the absorption cross section of PSII or ''spillover'' of excitation energy between the two photosystems. We report here on measurements of relative absorption cross sections of PSII under state I and state II light conditions. We simultaneously followed the yields of O/sub 2/ and the change in fluorescence yields, ..delta.. phi, as a function of flash energy using single turnover xenon flashes. Our data suggest that the effective absorption cross section of PSII does not change within +- 10% under physiological conditions in unpoisoned Chlorella pyrenoidosa. 13 refs., 3 figs.
- Research Organization:
- Brookhaven National Lab., Upton, NY (USA); National Inst. for Basic Biology, Okazaki (Japan)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6671933
- Report Number(s):
- BNL-39389; CONF-860808-12; ON: DE87008721
- Resource Relation:
- Conference: 7. international congress on photosynthesis, Providence, RI, USA, 10 Aug 1986; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
PHOTOSYNTHETIC REACTION CENTERS
ELECTRON TRANSFER
CHLORELLA
CROSS SECTIONS
FLUORESCENCE SPECTROSCOPY
ALGAE
EMISSION SPECTROSCOPY
MICROORGANISMS
PLANTS
SPECTROSCOPY
UNICELLULAR ALGAE
140505* - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)
550200 - Biochemistry