Uptake of [14C]sucrose in isolated minor-vein networks of Commelina benghalensis L |
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Authors: | val Bel A J E Koops A J |
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Institution: | (1) Department of Plant Physiology, Rijksuniversiteit Utrecht, Lange Nieuwstraat 106, NL-3512 PN Utrecht, The Netherlands |
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Abstract: | Maceration with pectinase (4.5h) of Commelina benghalensis L. leaves stripped at either side yielded isolated vein networks consisting of four to five secondary veins and tertiary cross veins (=minor veins). Examination with Evans Blue and injection of Fluorescein F showed that 80% of the veins were viable. Proof of normal functioning of isolated minor veins was that 14C]sucrose fed to an apical vein network attached to the remaining intact part of the leaf was absorbed and finally arrived in the petiole. Sucrose uptake by veins obeyed Michaelis-Menten kinetics (K
m 5·10-4 mol l-1; V
max (light) 3.2 mol h-1 g-1 fresh weight, V
max (dark) 1.5 mol h-1 g-1 fresh weight). A linear component, not inhibited by carbonylcyanide m-chlorophenylhydrazone and p-chloromercuribenzenesulfonic acid, was present. Maximal uptake took place at 5 mmol l-1 K+; concentrations of K+ higher than 10 mmol l-1 decreased the rate of uptake. The uptake rates by isolated veins and veins in situ (in disks) were in the same order of magnitude. Altogether, isolated veins promise to be a useful system for the study of loading.Abbreviations CCCP
carbonylcyanide m-chlorophenylhydrazone
- EDTA
ethylenediamine tetraacetic acid
- PCMBS
p-chloromercuribenzenesulfonic acid |
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Keywords: | Commelina Phloem loading Sucrose uptake Vein (isolation sucrose uptake) |
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