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Keywords:

  • Fructan synthesis;
  • kestose;
  • Lolium rigidum (annual ryegrass);
  • oligosaccharide;
  • sucrose

summary

  1. Top of page
  2. references

Accumulation of water-soluble carbohydrates (WSC) in leaves of intact seedlings of annual ryegrass (Lolium rigidum Gaudin cv. Wimmera) was studied using a novel model system. The roots and leaf bases of intact seedlings, grown in nutrient solution, were cooled to 5°C to reduce sink activity and the production of photosynthates was enhanced by continuous illumination of the plants. This resulted in accumulation of WSC in the shoots. Thin-layer chromatography showed the presence of a complex series of fructans, distinct from those found in tubers of Helianthus tuberosus. Two trisaccharides, 1-kestose and neokestose, were present in various proportions, but no 6-kestose was detected in the shoots. After feeding 14CO2 to the seedlings in a pulse-chase experiment, high specific radioactivity was measured in monosaccharides, sucrose and fructan oligosaccharide fractions to DP 5 within 1 hr. These fructan pools were rapidly turned over without significant accumulation of fructans during the first 16 h of the accumulation phase. Neokestose and 1-kestose contained equally high specific radioactivity, 1 h after feeding. These results indicated that neokestose was possibly as important as 1-kestose as a possible precursor for synthesis of fructan. Concentrations of WSC increased linearly from 2 to 14 mg g−1 f. Wt of the leaves after 16 h and reached a concentration of 30 mg g−1 f. wt after 64 h. Sucrose, glucose and fructose were the first sugars to be accumulated and reached concentrations of 10, 3.5 and 2.5 mg g−1 f. wt, respectively. Tri- and tetrasaccharide accumulated to measurable concentrations after approximately 16 h of treatment and reached concentrations of 2.5 and 2.0 mg g−1 f. wt, respectively. The appearance of these oligosaccharides occurred when sucrose and monosaccharides reached stable concentrations in the leaves, The WSC concentration declined at a rate of about 0.8 mg g−1 f. wt h−1, when the root temperature was raised to 24°C after 64 h and plants were darkened. The decline in WSC concentration was accompanied by a 70% decline in sucrose concentration and a decline in all other fructan concentrations, white the concentration of fructose increased 2-fold.

Abbreviations
DP

degree of polymerization

FFT

fructan-fructan fructosytransferase Fruf, fructofuranose

Glp

glucopyranose

HPLC

high performance liquid chromatography

Rt

relative mobility factor

SST

sucrose-sucrose fructosyl- transferase

TLC

thin-layer chromatography

WSC

water-soluble carbohydrates

references

  1. Top of page
  2. references
  • Cairns, A. J. & Pollock, C. J. (1988a). Fructan biosynthesis in excised leaves of Lolium temulentum L. I. Chromatographic characterization of oligofructans and their labelling patterns following 14CO2 feeding. New Phytologist 109, 399405.
  • Cairns, A. J. & Pollock, C. J. (1988b). Fructan biosynthesis in excised leaves of Lolium tremulentum L. II. Changes in fructosyltransferase activity following excision and application of inhibitors of gene expression. New Phytologist 109, 407413.
  • Cairns, A. J., Winters, A. & Pollock, C J. (1989). Fructan biosynthesis in excised leaves of Lolium temulentum L. III. A comparison of the in Vitro properties of fructosyltransferase activities with the characteristics of in vitro fructan accumulation. New Phytologist 112, 343352.
  • Edelman, J. & Jefford, T. G. (1968). The mechanism of fructosan metabolism in higher plants as exemplified in Helianthus tuberosus. New Phytologist 67, 517531.
  • Farrar, S. C. & Farrar, J. F. (1985). Carbon fluxes in leaf Wades of barley, New Phytologist 100, 271283.
  • Housley, T. L. & Pollock, C. J. (1985). Photosynthesis and carbohydrate metabolism in detached leaves of Lolium temulentum L. New Phytologist 99, 499507.
  • Labhart, C. H., Nösberger, J. & Nelson, C. J. (1983). Photosynthesis and degree of polymerization of fructan during reproductive growth of meadow fescue at two temperatures and two photon flux densities. Journal of Experimental Botany 34, 10371046.
  • Nilsson, U., ÖSte, R. & Jägerstad, M. (1987). Cereal fructans: hydrolysis by yeast invertase, in vitro and during fermentation. Journal of Cereal Science 6, 5360.
  • Pollock, C. J. (1982a). Patterns of turnover of fructans in leaves of Dactylis glomerata L. New Phytologist 90, 645650.
  • Pollock, C. J. (1982b). Oligosactharide intermediates of fructan synthesis in Lolium temulentum L. Phytochemistry 21, 24612465.
  • Pollock, C. J. (1984). Sucrose accumulation and the initiation of fructan biosynthesis in Lolium temulentum L. New Phytologist 96, 527534.
  • Pollock, C. J. (1986). Fructans and the metabolism of sucrose in vascular plants. New Phytologist 104, 124.
  • Shiomi, N. (1981). Purification and characterization of 6G-fructosyltransferase from the roots of asparagus (Asparagus officinalis L.). Carbohydrate Research 96, 281292.
  • Shiomi, K. (1982a). Reverse reactions of fructosyl transfer catalysed by asparagus 6G-fructosyltransferase. Carbohydrate Research 106, 166169.
  • Shiomi, N. (1982b). Purification and characterization of 1F-fructosyltransferase from the roots of asparagus [Asparagus officinalis L.). Carbohydrate Research 99, 157169.
  • Sims, I. M., Smouter, H., Pollock, C. J. & Simpson, R. J. (1991). The separation of complex mixtures of fructo-oligo-saccharides from plants. Plant Physiology and Biochemistry 29, 257267.
  • Smouter, H. & Simpson, R. J. (1989). Occurrence of fructans in the Gramineae (Poaceae). New Phytologist 111, 359368.
  • Straathof, A. J., Kieboom, A. P. G. & Vanberkkum, H. (1989). Invertase-catalysed fructosyl transfer in concentrated solutions of sucrose. Carbohydrate Research 146, 154159.
  • Tomasic, J., Jennings, H. J. & Glaudemas, C. P. J. (1978). Evidence for a single type of linkage in a fructofuranan from Lolium perenne. Carbohydrate Research 62, 127133.
  • Wagner, W., Keller, F. & Wiemken A. (1983). Fructan metabolism in cereals: induction in leaves and compartmentation in protoplasts and vacuoles. Zeitschrift für Pflanzen-physiologie 112, 359372.
  • Wagnur, W. & Wiemken, A. (1986a). Properties and cellular localization of fructan hydrolase in the leaves of barley (Hordeum vulgare L. ev Gerbel). Journal of Plant Physiology 123, 429439.
  • Wagner, W. & Wiemken, A. (1986b). Sugar-induced fructan synthesis in primary leaf blades of barley. In: Current Tapirs in Plant Biochemistry and Physiology, vol. 5 (Ed. by D. D.Randall), p. 196. University of Missouri, Columbia , USA .
  • Wagner, W. & Wiemken, A. (1987). Enzymology of fructan synthesis in grasses. Plant Physiology 85, 706710.
  • Wise, C. S., Dimleh, R. J., Davis, H. A. & Rist, C. E. (1955). Determination of easily hydrolyzable fructose units in dextran preparations. Analytical Chemistry 27, 3336.
  • Yemm, E. W. & Willis, A. J. (1954). The estimation of carbohydrates in plant extracts by anthrone. Biochemistry Journal 57, 508514.