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Phloem loading in ricinus cotyledons : sucrose pathways via the mesophyll and the apoplasm

Title data

Orlich, Gabriele ; Komor, Ewald:
Phloem loading in ricinus cotyledons : sucrose pathways via the mesophyll and the apoplasm.
In: Planta. Vol. 187 (1992) Issue 4 . - pp. 460-474.
ISSN 0032-0935
DOI: https://doi.org/10.1007/BF00199964

Abstract in another language

"Ricinus communis cv. Carmencita seedlings with their cotyledons incubated in sucrose solution and their hypocotyls cut to induce exudation of phloem sap, constitute a system of sucrose fluxes into and out of the cotyledons. This system was characterized with respect to quasi-steady-state conditions of sucrose uptake and export and then used to investigate the pathways of sucrose during phloem loading. The redistribution of C-14-labelled internal sucrose between the three ""compartments"", cotyledons (mesophyll), exudate (sieve tubes) and incubation medium (cell-wall space), was measured in the presence or absence of external non-labelled sucrose. It was found that mesophyll-derived labelled and external sucrose compete at uptake sites in the apoplasm. On the basis of the specific radioactivity of sucrose which reflects the proportionate intermixture of mesophyll-derived and external sucrose in the three ""compartments"", it was determined that about 50% of the sucrose exported is loaded directly from the apoplasm, while the other half takes the route via the mesophyll. It was confirmed that mesophyll-derived sucrose is released into the apoplasm, so that the existence of an indirect apoplasmic loading pathway is established. Calculations depending on the concentration gradients of labelled and non-labelled sucrose in the cell-wall space are presented to quantify tentatively the proportions of direct and indirect apoplasmic as well as symplasmic loading."

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER22543
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Biology > Chair Plant Physiology
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Biology
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 05 Feb 2016 07:23
Last Modified: 05 Feb 2016 07:23
URI: https://eref.uni-bayreuth.de/id/eprint/30445