Journal Article

Sugar Retrieval by Coats of Developing Seeds of <i>Phaseolus vulgaris</i> L. and <i>Vicia faba</i> L.

Raymond J. Ritchie, Sabine Fieuw-Makaroff and John W. Patrick

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 2, pages 163-172
Published in print February 2003 | ISSN: 0032-0781
Published online February 2003 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pcg022
Sugar Retrieval by Coats of Developing Seeds of Phaseolus vulgaris L. and Vicia faba L.

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Influxes of glucose, fructose and sucrose were characterised for coat cells of developing seeds of Phaseolus vulgaris L. and Vicia faba L. by monitoring uptake of [14C]sugars into excised seed-coat halves and two different protoplast populations derived from seed coats. Sugar influxes by the two populations of protoplasts were similar for each sugar species [sucrose > (fructose ≈ glucose)] and hexoses competed with sucrose. Concentration-dependent influxes of all three sugars by excised seed coats could be described by a simple directly proportional relationship between concentration ([S]) and uptake rate (v) in the physiological range of sugar concentrations (vA.[S]). Alternatively, with the exception of fructose influx by Vicia, all could be fitted to a Michaelis-Menten relationship, as could sucrose uptake by Vicia protoplasts. Apparent Km values were high (≈ 100–500 mM) compared with those reported for other systems. Sucrose transport was distinct from glucose and fructose transport in both species. Sugar influx was decreased by p-chloromercuribenzenesulfonic acid, carbonylcyanide m-chlorophenylhydrazone and erythrosin B. These responses are consistent with sugar/H+ symport acting to retrieve photoassimilates leaked to the apoplasm during post-sieve element transport within seed coats.

Keywords: Keywords: Phaseolus vulgaris L. — Protoplasts — Retrieval — Seed coat — Sugar/H+ symport — Vicia faba L.; Abbreviations: CCCP, carbonylcyanide m-chlorophenylhydrazone; EB, erythrosin B; PAR, photosynthetically active radiation; pCMBS, p-chloromercuribenzenesulfonic acid; PVP, polyvinyl pyrrolidine; pmf, proton motive force.

Journal Article.  7074 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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