Partitioning of photosynthetic electron flow between CO2 and O2 reduction in a C3 leaf (Phaseolus vulgaris L.) at different CO2 concentrations and during drought stress |
| |
Authors: | Gabriel Cornic Jean-Marie Briantais |
| |
Institution: | (1) Laboratoire d'écologie végétale, Université de Paris XI, F-91405 Orsay, France |
| |
Abstract: | Photosystem II chlorophyll fluorescence and leaf net gas exchanges (CO2 and H2O) were measured simultaneously on bean leaves (Phaseolus vulgaris L.) submitted either to different ambient CO2 concentrations or to a drought stress. When leaves are under photorespiratory conditions, a simple fluorescence parameter F/ Fm (B. Genty et al. 1989, Biochem. Biophys. Acta 990, 87–92; F = difference between maximum, Fm, and steady-state fluorescence emissions) allows the calculation of the total rate of photosynthetic electron-transport and the rate of electron transport to O2. These rates are in agreement with the measurements of leaf O2 absorption using 18O2 and the kinetic properties of ribulose-1,5bisphosphate carboxylase/oxygenase. The fluorescence parameter, F/Fm, showed that the allocation of photosynthetic electrons to O2 was increased during the desiccation of a leaf. Decreasing leaf net CO2 uptake, either by decreasing the ambient CO2 concentration or by dehydrating a leaf, had the same effect on the partitioning of photosynthetic electrons between CO2 and O2 reduction. It is concluded that the decline of net CO2 uptake of a leaf under drought stress is only due, at least for a mild reversible stress (causing at most a leaf water deficit of 35%), to stomatal closure which leads to a decrease in leaf internal CO2 concentration. Since, during the dehydration of a leaf, the calculated internal CO2 concentration remained constant or even increased we conclude that this calculation is misleading under such conditions.Abbreviations Ca, Ci
ambient, leaf internal CO2 concentrations
- Fm, Fo, Fs
maximum, minimal, steady-state fluorescence emission
- Fv
variable fluorescence emission
- PPFD
photosynthetic photon flux density
- qp, qN
photochemical, non-photochemical fluorescence quenching
- Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase |
| |
Keywords: | Chlorophyll fluorescence Drought stress Leaf (internal [CO2] net CO2 uptake) Phaseolus (photosynthesis) Photorespiration Photosynthesis (electron flow) |
本文献已被 SpringerLink 等数据库收录! |
|