Osmotic factors affecting sucrose storage and nobilisation in storage roots of Beta vulgaris L.
Osmotic factors affecting sucrose storage and nobilisation in storage roots of Beta vulgaris L.
The osmotic implications of the storage and mobilisation of sucrose in storage roots of beet (Beta vulgaris L.) have been investigated, using excised disks that were washed in aerated solutions of various compositions. Mannitol was used to vary the external osmotic pressure applied to the disks. Efflux analysis of 14C-mannitol showed that its behaviour was similar to that of the non-penetrating osmoticum 3H-inulin. Fresh disks contained high levels of sucrose, but after 24 h of washing, an acid invertase was induced that hydrolysed the sucrose of its constituent hexoses. The subsequent mobilisation of these hexoses was dependent on the external osmotic pressure. In hypotonic solutions, a proportion of all the major solutes was leaked from the disks, although the ability to retain both betanin and fluorescein diacetate indicated that membrane integrity was maintained. In increasingly hypertonic solutions, greater concentrations of hexoses were retained by the disks. These changes in solute concentrations resulted in adjustment of the turgor of the disks, but only those disks in 200mM mannitol maintained a constant turgor. When salts were added to the external solution these were absorbed by the disks. This induced mobilisation of the hexoses retained in the tissue and led to an increase in turgor that was independent of the external osmotic pressure. This effect was obtained with both KC1 and NaC1 either singly or in combination. The cations were accumulated as their chlorides. When supplied with both cations, the tissue showed sodium selectivity but this was turgor-dependent. The contribution of extracellular solute accumulation to turgor maintenance during sucrose storage was investigated using two methods to estimate extracellular water potentials of intact beets. The results were inconclusive but suggested that high-sucrose beets might have an increased ability to accumulate solutes in the apoplast. (D68635/86)
University of Southampton
1986
Perry, Caroline Anne
(1986)
Osmotic factors affecting sucrose storage and nobilisation in storage roots of Beta vulgaris L.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The osmotic implications of the storage and mobilisation of sucrose in storage roots of beet (Beta vulgaris L.) have been investigated, using excised disks that were washed in aerated solutions of various compositions. Mannitol was used to vary the external osmotic pressure applied to the disks. Efflux analysis of 14C-mannitol showed that its behaviour was similar to that of the non-penetrating osmoticum 3H-inulin. Fresh disks contained high levels of sucrose, but after 24 h of washing, an acid invertase was induced that hydrolysed the sucrose of its constituent hexoses. The subsequent mobilisation of these hexoses was dependent on the external osmotic pressure. In hypotonic solutions, a proportion of all the major solutes was leaked from the disks, although the ability to retain both betanin and fluorescein diacetate indicated that membrane integrity was maintained. In increasingly hypertonic solutions, greater concentrations of hexoses were retained by the disks. These changes in solute concentrations resulted in adjustment of the turgor of the disks, but only those disks in 200mM mannitol maintained a constant turgor. When salts were added to the external solution these were absorbed by the disks. This induced mobilisation of the hexoses retained in the tissue and led to an increase in turgor that was independent of the external osmotic pressure. This effect was obtained with both KC1 and NaC1 either singly or in combination. The cations were accumulated as their chlorides. When supplied with both cations, the tissue showed sodium selectivity but this was turgor-dependent. The contribution of extracellular solute accumulation to turgor maintenance during sucrose storage was investigated using two methods to estimate extracellular water potentials of intact beets. The results were inconclusive but suggested that high-sucrose beets might have an increased ability to accumulate solutes in the apoplast. (D68635/86)
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Published date: 1986
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Local EPrints ID: 461707
URI: http://eprints.soton.ac.uk/id/eprint/461707
PURE UUID: 999bd74f-d108-47f0-8a1f-0d79603e2ca0
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Date deposited: 04 Jul 2022 18:52
Last modified: 04 Jul 2022 18:52
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Author:
Caroline Anne Perry
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