Turgor-Regulated Sugar Release from the Source Leaves of Sugarbeet : Beta vulgaris L.

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概要

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• Under mild water stress conditions, a potential site of regulation for distribution of sucrose between osmotic adjustment and export may be at the mesophyll plasmalemma and/or tonoplast. This possibility was examined in attached leaves of sugarbeet (Beta vulgaris L.), labeled with ^<14>CO_2. Leaf discs were exposed to solutions containing 400 or 50 mM mannitol to generate "low" or "high" cellular turgor, respectively and release of labeled solutes was monitored. Response to changes in cell turgor was rapid and reversible. High turgor increased solute efflux rates to double those at low turgor conditions. Approximately 30% and 55% of the released label was in the sugar (sucrose and hexose) fractions at low and high turgor, respectively. Paramercuribenzene sulfonic acid (PCMBS) had no effect on efflux, but N-ethylmaleimide (NEM) and carbonylcyanide-m-chlorophenyl hydrazone (CCCP) enhanced efflux, especially at high turgor. Presence of unlabeled sucrose greatly enhanced efflux in a turgor-dependent manner; suggesting a sucrose exchange system. While influx across the plasmalemma is both turgor sensitive and carrier-mediated, turgor-regulated plasmalemma efflux did not appear to involve a carrier. Both the tonoplast and plasmalemma appeared to be involved in turgor-induced sugar efflux. Turgor-regulated efflux of solutes from vacuole-containing cells (mesophyll), may con-tribute to the establishment of a homeostatic turgor pressure in these cells.

• 日本植物生理学会の論文

著者

• Daie J

  Univ. Wisconsin Wisconsin Usa

• Daie Jaleh

  Crop Science Department, Lipman Hall, P. O. Box 231 Cook College, Rutgers Universlty

関連論文

• Does Apoplastic Sucrose Induce the Ability for Sucrose Loading in Developing Leaves of Sugarbeet?
• Turgor-Regulated Sugar Release from the Source Leaves of Sugarbeet : Beta vulgaris L.

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