Abstract
The characteristics of sorbitol and sucrose export out of mature leaves in seedlings of peach (Prunus persica L. Batsch cv GF 305) were investigated by simulating carbon fluxes through the leaf. Three treatments were employed: a control treatment and two treatments modifying leaf export, the latter using either shading or girdling. Photosynthesis and 14C partitioning into sorbitol and sucrose were measured during carbohydrate pool buildup at the beginning of the photoperiod, and the export rate of sorbitol and sucrose was modeled using a PSPICE (Simulation Program with Integrated Circuit Emphasis) simulator. The simulation allowed prediction of the resulting sorbitol and sucrose contents, which were compared to experimental carbohydrate contents. The apparent Km for sorbitol and sucrose phloem loading, estimated by carbon flux modeling, was 6.6 and 4 mol m-3, respectively. The predicted export capacity of the leaf, characterized by the estimated Vmax values for phloem loading of sorbitol and sucrose, was similar to the photosynthetic carbon flux measured under the leaf growth conditions. This export capacity was enhanced in plants in which all leaves except those studied were shaded. The mature leaf had a higher storage capacity for sorbitol than for sucrose in control plants, especially in the girdled treatment. Sucrose content appears to be tightly regulated.
Full Text
The Full Text of this article is available as a PDF (892.8 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bush D. R. Proton-Coupled Sucrose Transport in Plasmalemma Vesicles Isolated from Sugar Beet (Beta vulgaris L. cv Great Western) Leaves. Plant Physiol. 1989 Apr;89(4):1318–1323. doi: 10.1104/pp.89.4.1318. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Goldschmidt E. E., Huber S. C. Regulation of photosynthesis by end-product accumulation in leaves of plants storing starch, sucrose, and hexose sugars. Plant Physiol. 1992 Aug;99(4):1443–1448. doi: 10.1104/pp.99.4.1443. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Moing A., Carbonne F., Rashad M. H., Gaudillère J. P. Carbon fluxes in mature peach leaves. Plant Physiol. 1992 Dec;100(4):1878–1884. doi: 10.1104/pp.100.4.1878. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Molz F. J., Kerns D. V., Peterson C. M., Dane J. H. A circuit analog model for studying quantitative water relations of plant tissues. Plant Physiol. 1979 Nov;64(5):712–716. doi: 10.1104/pp.64.5.712. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Riens B., Lohaus G., Heineke D., Heldt H. W. Amino Acid and sucrose content determined in the cytosolic, chloroplastic, and vacuolar compartments and in the Phloem sap of spinach leaves. Plant Physiol. 1991 Sep;97(1):227–233. doi: 10.1104/pp.97.1.227. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Riesmeier J. W., Hirner B., Frommer W. B. Potato sucrose transporter expression in minor veins indicates a role in phloem loading. Plant Cell. 1993 Nov;5(11):1591–1598. doi: 10.1105/tpc.5.11.1591. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Riesmeier J. W., Willmitzer L., Frommer W. B. Isolation and characterization of a sucrose carrier cDNA from spinach by functional expression in yeast. EMBO J. 1992 Dec;11(13):4705–4713. doi: 10.1002/j.1460-2075.1992.tb05575.x. [DOI] [PMC free article] [PubMed] [Google Scholar]