Efficiency of photosynthesis

Kok, Bessel

doi:10.1007/978-3-642-94798-8_22

Cited by 28 publications

(26 citation statements)

References 163 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Only time will tell if tbe Z-scheme will be as well regarded in 2092 as it is now but, at least for the moment, there is a huge body of evidence, derived from all manner of different measurements (see e.g. Kok, 1960), which compels us to take it seriously.…”

Section: The Z-schemementioning

confidence: 99%

Tansley Review No. 36 Excited leaves

Walker

1992

New Phytologist

View full text Add to dashboard Cite

SUMMARY Photosynthesis is largely to do with energy transduction; the conversion of light energy into electrical energy into chemical energy. Precisely how much light energy is needed to bring about the reduction of one molecule of carbon dioxide and the release of one molecule of oxygen (the quantum requirement) is a matter of fundamental importance and one which has attracted much past controversy. This article concludes that a minimum quantum requirement of eight, as demanded by the Z‐scheme, is obviously consistent with much contemporary work which puts the measured value for C3 leaves close to nine. Moreover, while values of less than eight (obtained in some circumstances with micro‐organisms), are a reminder that nothing is beyond challenge they are not, in the absence of confirmation and extension, sufficiently compelling to demand rejection of either the Z‐scheme or current measuring procedures. This article also shows why, even if the underlying minimum requirement was now accepted beyond all reasonable doubt, there would still be very good reasons for continuing, indefinitely, to measure actual photosynthetic efficiency in the natural environment. It discusses some of the implications of the fact that all plants, if not stressed, appear to photosynthesize at the same rate in low light. It explains the role of fluorescence in its relation to quantum yield, the possibility that the rate of photosynthesis might be determined from fluorescence measurements alone, and that a combination of fluorescence and gas exchange measurements could provide new information about the manner in which ‘dark respiration’ is affected by light. It indicates how contemporary interest in all of these matters has focused attention on the necessity for safe dissipation of excitation energy by leaves and on the manner by which this might be achieved.

show abstract

Section: The Z-schemementioning

confidence: 99%

Tansley Review No. 36 Excited leaves

Walker

1992

New Phytologist

View full text Add to dashboard Cite

show abstract

“…Both investigations show widely diverging values of the measured photon requirement which varies in conjunction with changes in the gas exchange quotient (COg flux divided by the Og flux). In order to avoid confusing experimental observations, which may have been made under suboptimal conditions, with the true minimum photon requirement, we will call the measured values apparent photon requirements (^co o) ^^ distinguish them from the true minimum value (^cog ^^ Og)-This formality is necessary because much of the controversy over the correct value of the minimum photon requirement has been exacerbated by questions regarding methodological problems and the interpretation of results (Nishimura, Whittingham & Emerson, 1951;Kok, 1952Kok, , 1960Emerson & Chalmers, 1955) and because the reactant (i.e. COg) and product (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Warburg & Burk (1950) placed more emphasis on values of O^J obtained at high values of the gas exchange quotient and Yuan et al (1955) ignored the variation in OQ^ and used an average value. Pirt (1986) maintains that more emphasis should be placed on measurements obtained at low values of y because this is the value for growth of microalgae using nitrate as a nitrogen source (see also Kok, 1960;Myers, 1980). Pirt (1986) interprets the convergence of both data sets on the same apparent photon requirement, when physiological conditions are representative of growing cells, as evidence that the true minimum photon requirement is 6 mol photons mol~^ Og.…”

Section: Introductionmentioning

confidence: 99%

The Minimum Photon Requirement for Photosynthesis

Geider

1987

New Phytologist

View full text Add to dashboard Cite

SUMMARYVariations in the apparent photon requirement for photosynthesis (cb,) o"" (^ol) ^^ *^^ ^^^ô f Warburg & Burk (1950) and Yuan, Evans & Daniels (1955) can be ascribed to changes in O2 uptake and energy-dependent processes which result in aberrant photon requirements in organisms subjected to non-optimal conditions. The increase in 05, with increases in the gas exchange quotient (7) in the observations of Yuan et al. (1955) is consistent with increases in photorespiratory production of glycollate, whilst changes in ^5l ^^^ *^CO2 '^ ^^^ results of Warburg & Burk (1950) can be explained by a variable Kok effect associated with nitrate assimilation at low light levels. When these Og and energy-dependent processes are minimal, the lowest values should be observed. The minimum value obtained when Chlorella is photosynthesizing under optimal conditions is 6 mol photons mol"^ Og. These results provide direct independent evidence for a photon requirement for photosynthesis of less than 8 mol photons mol"^ Og. Such a value is not consistent with the Z scheme of photosynthesis.

show abstract

“…This fraction is photosynthetically stored radiation (PSR) which is the irradiance equivalent of carbon assimilation. The minimum number of photons required to produce PSR can be computed from the minimal quantum requirement of 10 moles of photons needed to reduce 1 mole of carbon (Kok 1960). For 22 April (station-cast 19.50), PSR was determined from 12-h in situ carbon assimilation measurements to be 0.06 10 moles of reduced C mW2, equivalent to 0.6 1 moles photons m-2.…”

mentioning

confidence: 99%

Estimation of a photon budget for the upper ocean in the Sargasso Sea

Smith

Marra

Perry

et al. 1989

Limnology & Oceanography

View full text Add to dashboard Cite

A photon budget based on the quanta absorbed and subsequent biological utilization is computed for a site in the northwestern Sargasso Sea in spring. The budget includes sources, transitions, and sinks for photosynthetically available radiation (PAR). The attentuation of PAR is partitioned into separate components and the loss caused by each component is estimated as a function of depth in the upper 100 m. The major sources of attenuation to PAR include seawater (35-76%), total particulate material (20-65%), and dissolved organic material (O-l 3%). The total particulate material attentuation could be partitioned into attenuation of phytoplankton (12-39%) and of detrital material (g-27%). Although the greatest fraction of photons is absorbed by water, all the variability within the budget is caused by biological processes. Source terms include bioluminescence and chlorophyll a fluorescence, which are orders of magnitude less than radiant energy attenuation, but they are detectable and biologically significant. This photon budget is an estimate, on a quantum basis, of how radiant energy is absorbed and how various fractions are converted to chemical energy or lost to nonphotosynthetic processes. The budget serves to focus on sources, transitions, and sinks of photons and elucidate the mechanisms linking biological processes and ocean optical properties; to identify the major absorbers in the ocean and quantify their relative influence; to demonstrate an accounting with respect to the penetration of radiant energy into natural waters and point to major assumptions and uncertainties in our current estimate; and to establish a perspective that can serve as a basis for the predictive linkage of optical variability and bioluminescence. Acknowledgments

show abstract

Efficiency of photosynthesis

Cited by 28 publications

References 163 publications

Tansley Review No. 36 Excited leaves

Tansley Review No. 36 Excited leaves

The Minimum Photon Requirement for Photosynthesis

Estimation of a photon budget for the upper ocean in the Sargasso Sea

Contact Info

Product

Resources

About