Plant Physiology 75:95-101 (1984)
© 1984 American Society of Plant Biologists
Articles
Kok Effect and the Quantum Yield of Photosynthesis 1
Light Partially Inhibits Dark Respiration
Robert E. Sharp,
Mark A. Matthews2 and
John S. Boyer
Department of Plant Biology, University of Illinois, Urbana, Illinois 61801,
Department of Agronomy, University of Illinois, Urbana, Illinois 61801,
United States Department of Agriculture/Agricultural Research Service, University of Illinois, Urbana, Illinois 61801
The linear response of photosynthesis to light at low photon flux densities is known to change abruptly in the vicinity of the light compensation point so that the quantum yield seems to decrease as radiation increases. We studied this `Kok effect' in attached sunflower (Helianthus annuus L. cv IS894) leaves using gas exchange techniques. The effect was present even though respiration was constant in the dark. It was observed at a similar photon flux density (7 to 11 micromole photons per square meter per second absorbed photosynthetically active radiation) despite a wide range of light compensation points as well as rates of photosynthesis. The effect was not apparent when photorespiration was inhibited at low pO2 (1 kilopascal), but this result was complicated because dark respiration was quite O2-sensitive and was partially suppressed under these conditions. The Kok effect was observed at saturating pCO2 and, therefore, could not be explained by a change in photorespiration. Instead, the magnitude of the effect varied as dark respiration varied in a single leaf, and was minimized when dark respiration was minimized, indicating that a partial suppression of dark respiration by light is responsible. Quantum yields measured at photon flux densities between 0 and 7 to 11 micromole photons per square meter per second, therefore, represent the combined yields of photosynthesis and of the suppression of a component of dark respiration by light. This leads to an overestimate of the quantum yield of photosynthesis. In view of these results, quantum yields of photosynthesis must be measured (a) when respiration is constant in the dark, and (b) when dark respiration has been inhibited either at low pO2 to eliminate most of the light-induced suppression of dark respiration or at photon flux densities above that required to saturate the light-induced suppression of dark respiration. Significant errors in quantum yields of photosynthesis can result in leaves exhibiting this respiratory behavior if these principles are not followed.
2 Present address: Department of Viticulture and Enology, University of California, Davis, CA 95616.
1 Supported by National Science Foundation Grant PCM 79-09790 (to J. S. B.).
This article has been cited by other articles:
|
|
|
|
 
J. B. Skillman
Quantum yield variation across the three pathways of photosynthesis: not yet out of the dark
J. Exp. Bot.,
May 1, 2008;
59(7):
1647 - 1661.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
G. Tcherkez, G. Cornic, R. Bligny, E. Gout, and J. Ghashghaie
In Vivo Respiratory Metabolism of Illuminated Leaves
Plant Physiology,
July 1, 2005;
138(3):
1596 - 1606.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. M. FRANTZ, N. N. COMETTI, and B. BUGBEE
Night Temperature has a Minimal Effect on Respiration and Growth in Rapidly Growing Plants
Ann. Bot.,
July 1, 2004;
94(1):
155 - 166.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. Haupt-Herting, K. Klug, and H. P. Fock
A New Approach to Measure Gross CO2 Fluxes in Leaves. Gross CO2 Assimilation, Photorespiration, and Mitochondrial Respiration in the Light in Tomato under Drought Stress
Plant Physiology,
May 1, 2001;
126(1):
388 - 396.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
X. Wang, J. D. Lewis, D. T. Tissue, J. R. Seemann, and K. L. Griffin
Effects of elevated atmospheric CO2 concentration on leaf dark respiration of Xanthium strumarium in light and in darkness
PNAS,
February 27, 2001;
98(5):
2479 - 2484.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
