Evidence for the presence of a sucrose carrier in immature sugar beet tap roots. [Beta vulgaris L]
- Rutgers Univ., New Brunswick, NJ (USA)
The objectives of this work were to determine the path of phloem unloading and if a sucrose carrier was present in young sugar beet (Beta vulgaris L.) taproots. The approach was to exploit the characteristics of the sucrose analog, 1{prime}-fluorosucrose (F-sucrose) which is a poor substrate for acid invertase but is a substrate for sucrose synthase. Ten millimolar each of ({sup 3}H) sucrose and ({sup 14}C)F-sucrose were applied in a 1:1 ratio to an abraded region of an attached leaf for 6 hours. ({sup 14}C)F-sucrose was translocated and accumulated in the roots at a higher rate than ({sup 3}H)sucrose. This was due to ({sup 3}H)sucrose hydrolysis along the translocation path. Presence of ({sup 3}H)hexose and ({sup 14}C)F-sucrose in the root apoplast suggested apoplastic sucrose unloading with its subsequent hydrolysis. Labeled F-sucrose uptake by root tissue discs exhibited biphasic kinetics and was inhibited by unlabeled sucrose, indicating that immature roots have the ability for carrier-mediated sucrose transport from the apoplast. Collectively, in vivo and in vitro data indicate that despite sucrose hydrolysis by the wall-bound invertase, sucrose hydrolysis is not entirely essential for sugar accumulation in this tissue.
- OSTI ID:
- 7066264
- Journal Information:
- Plant Physiology; (USA), Journal Name: Plant Physiology; (USA) Vol. 86:2; ISSN 0032-0889; ISSN PLPHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
AGE DEPENDENCE
BIOCHEMICAL REACTION KINETICS
CARBOHYDRATES
CARBON 14 COMPOUNDS
CHEMICAL REACTIONS
DECOMPOSITION
DISACCHARIDES
ENZYME ACTIVITY
HYDROGEN COMPOUNDS
HYDROLYSIS
INHIBITION
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
LEAVES
LYSIS
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
REACTION KINETICS
ROOTS
SACCHARIDES
SACCHAROSE
SOLVOLYSIS
TRACER TECHNIQUES
TRANSLOCATION
TRITIUM COMPOUNDS