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Photon requirement for O 2 ‐Revolution in red (λ= 680 nm) light for some C 3 and C 4 plants and a C 3 –C 4 intermediate species *
Author(s) -
OSBORNE B. A.
Publication year - 1994
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1994.tb00277.x
Subject(s) - thylakoid , photon , mixotroph , electron transport chain , chemistry , botany , analytical chemistry (journal) , biology , chloroplast , physics , optics , biochemistry , genetics , bacteria , gene , heterotroph , chromatography
Photon requirements for O 2 ‐evolution in red (λ=680nm) light (Ф r ) were measured for six C 3 species, one C 3 ‐like, C 3 –C 4 intermediate species, and three C 4 species, including examples of NADP‐malic enzyme and PEP‐carboxykinase C 4 sub‐groups. Variation in Ф r within the C 3 species was small with a mean value of 7.96 ±0.12 mol photon mol −1 O 2 , whereas the mean value for the C 4 species was 12.27± 1.53 mol photon mol −1 O 2 , with the lowest value, 9.24 ±0.13 mol photon mol −1 O 2 , for the PEP‐carboxykinase C 4 species Spartina townsendii. The C 3 –C 4 intermediate species Panicum milioides had a value of 9.05 ±0.29 mol photon mol −1 O 2 , approximately 1 mol photon mol −1 O 2 greater than the C 3 species. The possibility that this extra cost is due to PEP‐carboxylase‐dependent recycling of CO 2 is discussed. No correlation was found between Ф r and chlorophyll content or leaf absorptance. Based on white (Ф W ) and red light measurements of the photon requirement, values in red light were approximately 20% higher than white‐light estimates. These results are discussed with reference to accepted mechanisms of energy transduction in thylakoid membranes (Z‐scheme), expected inefficiencies and losses during light‐harvesting and electron transport reactions, and the influence of respiratory processes.