ISSN:
1432-2048
Keywords:
Commelina
;
Phloem loading
;
Sucrose uptake
;
Vein (isolation, sucrose uptake)
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
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 μmol h-1 g-1 fresh weight, V max (dark) 1.5 μmol 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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00402947
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