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THE MINIMUM PHOTON REQUIREMENT FOR PHOTOSYNTHESIS
Author(s) -
OSBORNE BRUCE A.,
GEIDER RICHARD J.
Publication year - 1987
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1987.tb00164.x
Subject(s) - photosynthesis , photon , physics , chemistry , nitrate , botany , biology , ecology , quantum mechanics
S ummary Variations in the apparent photon requirement for photosynthesis (Φ −1 co 2 ) or (Φ −1 co 2 ) in the data of Warburg & Burk (1950) and Yuan, Evans & Daniels (1955) can be ascribed to changes in O 2 uptake and energy‐dependent processes which result in aberrant photon requirements in organisms subjected to non‐optimal conditions. The increase in Φ −1 co 2 with increases in the gas exchange quotient (γ) in the observations of Yuan et al. (1955) is consistent with increases in photorespiratory production of glycollate, whilst changes in Φ −1 co 2 and Φ −1 co 2 in the results of Warburg & Burk (1950) can be explained by a variable Kok effect associated with nitrate assimilation at low light levels. When these O 2 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 −1 O 2 . These results provide direct independent evidence for a photon requirement for photosynthesis of less than 8 mol photons mol −1 O 2 . Such a value is not consistent with the Z scheme of photosynthesis.