Abstract
During C4 photosynthesis, CO2 is released in bundle-sheath cells by decarboxylation of C4 acids and then refixed via ribulose-1,5-bisphosphate carboxylase. In this study we examined the efficiency of this process by determining the proportion of the released CO2 that diffuses back to mesophyll cells instead of being refixed. This leak of CO2 was assessed by determining the amount of 14CO2 released from leaves during a chase in high [12CO2] following a 70-s pulse in 14CO2. A computer-based analysis of the time-course curve for 14CO2 release indicated a first-order process and provided an estimate of the initial velocity of 14CO2 release from leaves. From this value and the net rate of photosynthesis determined from the 14CO2 fixed in the pulse, the CO2 leak rate from bundle-sheath cells (expressed as a percentage of the rate of CO2 production from C4 acids) could be deduced. For nine species of Gramineae representing the different subgroups of C4 plants and two NAD-malic enzyme-type dicotyledonous species, the CO2 leak ranged between 8 and 14%. However, very high CO2 leak rates (averaging about 27%) were recorded for two NADP-malic enzyme-type dicotyledonous species of Flaveria. The results are discussed in terms of the efficiency of C4 photosynthesis and observed quantum yields.
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Selected References
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- Brown R. H., Byrd G. T. Estimation of Bundle Sheath Cell Conductance in C4 Species and O2 Insensitivity of Photosynthesis. Plant Physiol. 1993 Dec;103(4):1183–1188. doi: 10.1104/pp.103.4.1183. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ehleringer J., Pearcy R. W. Variation in Quantum Yield for CO(2) Uptake among C(3) and C(4) Plants. Plant Physiol. 1983 Nov;73(3):555–559. doi: 10.1104/pp.73.3.555. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Furbank R. T., Hatch M. D. Mechanism of c(4) photosynthesis: the size and composition of the inorganic carbon pool in bundle sheath cells. Plant Physiol. 1987 Dec;85(4):958–964. doi: 10.1104/pp.85.4.958. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Furbank R. T., Jenkins C. L., Hatch M. D. CO(2) Concentrating Mechanism of C(4) Photosynthesis: Permeability of Isolated Bundle Sheath Cells to Inorganic Carbon. Plant Physiol. 1989 Dec;91(4):1364–1371. doi: 10.1104/pp.91.4.1364. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Grantz D. A., Zeiger E. Stomatal responses to light and leaf-air water vapor pressure difference show similar kinetics in sugarcane and soybean. Plant Physiol. 1986 Jul;81(3):865–868. doi: 10.1104/pp.81.3.865. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hatch M. D. Mechanism of C4 photosynthesis in Chloris gayana: pool sizes and kinetics of 14CO2 incorporation into 4-carbon and 3-carbon intermediates. Arch Biochem Biophys. 1979 Apr 15;194(1):117–127. doi: 10.1016/0003-9861(79)90601-5. [DOI] [PubMed] [Google Scholar]
- Hatch M. D., Slack C. R. Photosynthesis by sugar-cane leaves. A new carboxylation reaction and the pathway of sugar formation. Biochem J. 1966 Oct;101(1):103–111. doi: 10.1042/bj1010103. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hatch M. D. The C 4 -pathway of photosynthesis. Evidence for an intermediate pool of carbon dioxide and the identity of the donor C 4 -dicarboxylic acid. Biochem J. 1971 Nov;125(2):425–432. doi: 10.1042/bj1250425. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jenkins C. L., Furbank R. T., Hatch M. D. Inorganic Carbon Diffusion between C(4) Mesophyll and Bundle Sheath Cells: Direct Bundle Sheath CO(2) Assimilation in Intact Leaves in the Presence of an Inhibitor of the C(4) Pathway. Plant Physiol. 1989 Dec;91(4):1356–1363. doi: 10.1104/pp.91.4.1356. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jenkins C. L., Furbank R. T., Hatch M. D. Mechanism of c(4) photosynthesis: a model describing the inorganic carbon pool in bundle sheath cells. Plant Physiol. 1989 Dec;91(4):1372–1381. doi: 10.1104/pp.91.4.1372. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Morison J. I., Gifford R. M. Stomatal sensitivity to carbon dioxide and humidity: a comparison of two c(3) and two c(4) grass species. Plant Physiol. 1983 Apr;71(4):789–796. doi: 10.1104/pp.71.4.789. [DOI] [PMC free article] [PubMed] [Google Scholar]