Articles
SUGAR UPTAKE AND METABOLISM IN TISSUE CULTURED POTATO PLANTLETS CULTURED IN LIQUID MEDIUM
Article number
748_36
Pages
265 – 273
Language
English
Abstract
The sucrose uptake and metabolism of potato (Solanum tuberosum, Norland) cultivated in vitro were studied to understand why photosynthesis is weak and there is poor adaptation of the plantlets upon transfer from in vitro to ex vitro (acclimatization) conditions.
The goal of this work is to follow the fate of absorbed medium sugar in different plant parts.
We have thus applied a special tagging technique by which asymmetrically labelled sucrose (marked on the fructose only) was fed for 1 hour to potato plantlets cultured in vitro.
The plantlets were cultivated on the MS liquid medium containing 0 g.L-1 (autotrophic) or 30 g.L-1 sucrose (mixotrophic) during 10 days.
The plantlets were transferred on the MS liquid medium containing 20 g.L-1 sucrose and 12,000 µCi.L-1 of asymmetrical tritiated sucrose, marked on the fructose (G-F*). After a 1 h incubation (pulse), the plantlets were transferred in the MS medium (chase) with 20 g.L-1 sucrose.
Radioactive soluble sugars were separated by HPLC and measured after intervals of 0, 1, 2, 3, 6 and 12 h.
Results show that the quantity of total marked sugars found in the medium of autotrophic plants cultivated on 0% sucrose was twice as much as that of the plantlets fed with 3% sucrose (mixoautotophic plantlets). Interestingly, labelled glucose is presented in the culture medium which indicating that asymmetrical sucrose was absorbed, metabolized and secreted by the roots.
In general, the quantity of total marked sugars found in mixoautotrophic plantlets was larger than that of the autotrophic plantlets and hexoses (marked fructose) were more abundant than sucrose.
Sugars did not accumulate in the leaves of the autotrophic plantlets.
Sucrose is absorbed but is then hydrolyzed to fructose and glucose which move throughout the plantlets.
The leaves of the autotrophic plantlets are not active sinks for fructose.
On the other hand, the mixotrophic plantlets absorb sucrose and accumulate fructose in their leaves.
The goal of this work is to follow the fate of absorbed medium sugar in different plant parts.
We have thus applied a special tagging technique by which asymmetrically labelled sucrose (marked on the fructose only) was fed for 1 hour to potato plantlets cultured in vitro.
The plantlets were cultivated on the MS liquid medium containing 0 g.L-1 (autotrophic) or 30 g.L-1 sucrose (mixotrophic) during 10 days.
The plantlets were transferred on the MS liquid medium containing 20 g.L-1 sucrose and 12,000 µCi.L-1 of asymmetrical tritiated sucrose, marked on the fructose (G-F*). After a 1 h incubation (pulse), the plantlets were transferred in the MS medium (chase) with 20 g.L-1 sucrose.
Radioactive soluble sugars were separated by HPLC and measured after intervals of 0, 1, 2, 3, 6 and 12 h.
Results show that the quantity of total marked sugars found in the medium of autotrophic plants cultivated on 0% sucrose was twice as much as that of the plantlets fed with 3% sucrose (mixoautotophic plantlets). Interestingly, labelled glucose is presented in the culture medium which indicating that asymmetrical sucrose was absorbed, metabolized and secreted by the roots.
In general, the quantity of total marked sugars found in mixoautotrophic plantlets was larger than that of the autotrophic plantlets and hexoses (marked fructose) were more abundant than sucrose.
Sugars did not accumulate in the leaves of the autotrophic plantlets.
Sucrose is absorbed but is then hydrolyzed to fructose and glucose which move throughout the plantlets.
The leaves of the autotrophic plantlets are not active sinks for fructose.
On the other hand, the mixotrophic plantlets absorb sucrose and accumulate fructose in their leaves.
Publication
Authors
A. Badr, Y. Desjardins
Keywords
micropropagation, acclimatization, autotrophy, mixotrophy, asymmetrically, HPLC
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