RT Journal Article
SR Electronic
T1 Partitioning of Noncyclic Photosynthetic Electron Transport to O<sub>2</sub>-Dependent Dissipative Processes as Probed by Fluorescence and CO<sub>2</sub> Exchange
JF Plant Physiology
JO Plant Physiol.
FD American Society of Plant Biologists
SP 1322
OP 1328
DO 10.1104/pp.90.4.1322
VO 90
IS 4
A1 Peterson, Richard B.
YR 1989
UL http://www.plantphysiol.org/content/90/4/1322.abstract
AB The partitioning of noncyclic photosynthetic electron transport between net fixation of CO2 and collective O2-dependent, dissipative processes such as photorespiration has been examined in intact leaf tissue from Nicotiana tabacum. The method involves simultaneous application of CO2 exchange and pulse modulated fluorescence measurements. As either irradiance or CO2 concentration is varied at 1% O2 (i.e. absence of significant O2-dependent electron flow), the quantum efficiency of PSII electron transport (φse) with CO2 as the terminal acceptor is a linear function of the ratio of photochemical:nonphotochemical fluorescence quenching coefficients (i.e. qQ:qNP). When the ambient O2 concentration is raised to 20.5% or 42% the qQ:qNP is assumed to predict the quantum efficiency of total noncyclic electron transport (φ′se). A factor which represents the proportion of electron flow diverted to the aforementioned dissipative processes is calculated as (φ′se − φse)/φ′se where φse is now the observed quantum efficiency of electron transport in support of net fixation of CO2. Examination of changes in electron allocation with CO2 and O2 concentration and irradiance at 25°C provides a test of the applicability of the Rubisco model to photosynthesis in vivo.