Abstract
Abstract Parallel measurements of contents of photosynthetic intermediates, activities of enzymes of photosynthetic carbon assimilation, gas-exchange rates and components of chlorophyll-fluorescence quenching in leaves of C4 plants are considered in relation to changes in photon flux density (PFD) and CO2. The influence of varying light and CO2 concentration upon changes in the amounts of phosphoenolpyruvate (PEP) in leaves of C4 plants during steady-state photosynthesis are interpreted in terms of the regulatory properties of PEP carboxylase and in terms of feedback interactions between the Calvin cycle and the C4 cycle. Relations between electron transport and carbon assimilation are discussed in terms of the regulation of the supply of ATP and NADPH and the demands of carbon assimilation. In low light these relations differ in C3 and C4 plants. The lag in photosynthetic carbon assimilation in maize that follows a decrease in PFD has been analysed. The changes that occur in enzyme activities, metabolites and components of chlorophyll-fluorescence quenching following the transition from high to low light indicate that diminished production of ATP and NADPH is responsible for the lag in photosynthetic carbon assimilation and may reflect a stimulation of cyclic electron flow to make up a deficit in ATP.
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Claims 4
Claim · model-written summary
Low-light relations between electron transport and carbon assimilation differ between C3 and C4 plants.
Verbatim
e0“In low light these relations differ in C3 and C4 plants”
Claim · model-written summary
A drop in photon flux density produces a lag in maize photosynthetic carbon assimilation.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The lag in photosynthetic carbon assimilation in maize that follows a decrease in PFD has been analysed”
Claim · model-written summary
The changes after high-to-low light suggest diminished ATP and NADPH production causes the assimilation lag.
Verbatim
e0“The changes that occur in enzyme activities, metabolites and components of chlorophyll-fluorescence quenching following the transition from high to low light indicate that diminished production of ATP and NADPH is responsible for the lag in photosynthetic carbon assimilation”
t0“C4 plants”
Claim · model-written summary
The low-light changes may reflect stimulation of cyclic electron flow to address an ATP deficit.
Verbatim
e0“may reflect a stimulation of cyclic electron flow to make up a deficit in ATP”
t0“C4 plants”