title: Sugar retrieval by coats of developing seeds of Phaseolus vulgaris L. and Vicia faba L.
abstract: 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 [(14)C]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 approximately 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 (v approximately A.[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 K(m) values were high ( approximately 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.
authors.affiliation: School of Biological Sciences A-08, University of Sydney, NSW 2006, Australia.
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Ritchie
authors.forename: Sabine
authors.initials: S
authors.lastname: Fieuw-Makaroff
authors.forename: John W
authors.initials: JW
authors.lastname: Patrick
mesh_terms: D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000465:Algorithms; D001692:Biological Transport / Q000187:drug effects; D050260:Carbohydrate Metabolism; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002470:Cell Survival / Q000502:physiology; D004923:Erythrosine / Q000494:pharmacology; D005632:Fructose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D008954:Models, Biological; D027805:Phaseolus / Q000254:growth & development / Q000378:metabolism*; D019441:Plant Epidermis / Q000378:metabolism; D017494:Proton Pumps / Q000187:drug effects / Q000378:metabolism; D011523:Protoplasts / Q000502:physiology; D012639:Seeds / Q000254:growth & development / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism; D031307:Vicia faba / Q000254:growth & development / Q000378:metabolism*
chemical_list: D017494:Proton Pumps; D005632:Fructose; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D013395:Sucrose; D002731:4-Chloromercuribenzenesulfonate; D005947:Glucose; D004923:Erythrosine