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Mannitol transport and suitability as an osmoticum in root cells
Author(s) -
Cram W. J.
Publication year - 1984
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1984.tb06346.x
Subject(s) - mannitol , cytoplasmic streaming , hordeum vulgare , cell wall , vacuole , biophysics , cytoplasm , chemistry , ion transporter , botany , biology , biochemistry , membrane , poaceae
Fluxes of mannitol across plasmalemma and tonoplast of excised carrot storage root tissue were measured using compartmental analysis of 14 C tracer exchange. Mannitol metabolism and the contribution of [ 14 C]‐labelled metabolites to efflux was shown to be small. Similar but less extensive measurements were made on red beet ( Beta vulgaris L.), barley ( Hordeum vulgare L.) and maize ( Zea mays L.) roots. Calculated values of the reflection coefficient for mannitol were close to one, but, despite this, the inflow of mannitol was sufficient to dissipate the mannitol concentration gradient between inside and outside the cells within the time it takes them to adjust vacuolar concentrations. Thus mannitol is not suitable as an osmoticum in osmotic adjustment experiments in these root tissues. Mannitol flows appear to be passive. Permeability to mannitol (about 10 −10 m s −1 is greater at the plasmalemma than at the tonoplast in carrot, and this would tend to cause the cytoplasm to swell. The implications for the control of cytoplasmic volume are discussed.