Philip A. Harrison

Characterization of fructan oligomers from species of the genus Allium L.

Summary Storage tissue of leaf bases from several species of the genus Allium [ A. cepa L. var. cepa (onion, 6 cvs.), A. cepa L. var. ascalonicum (shallot, 7 cvs.), A. ampeloprasum L. var. porrum (leek, 3 cvs.), A. schoenoprasum L. (chives), A. sativum L. (garlic), A. fistulosum L. (Japanese bunching onion/Welsh onion), A. tuberosum Rottl. ex. spr. (Chinese chives/Nira), and other species] were analyzed to determine their water soluble carbohydrate composition. The Allium species analyzed can be divided into three groups according to their fructan profiles: 1. Those with relatively high amounts of larger fructan polymers, 2. Those with relatively high amounts of small fructan polymers up to a degree of polymerization of about 15, and 3. Those with both large and small fructan polymers. Four major fructan series with exclusively (2→1) fructosyl-fructose linkages have been characterized that are typical of those Allium species containing small fructan polymers. They are: 1. an inulin series with the general formula: G - 1 , 2 - F - 1 , ( 2 - F - 1 ) n , 2 - F ( G - 1 , 2 - F = s u c r o s e ) , 2. a neokestose-based series with chain elongation only at the glucose end of the original sucrose molecule: F - 2 , ( 1 - F - 2 ) m , 1 - F - 2 , 6 - G - 1 , 2 - F , 3. a neokestose-based series with elongation from both sides of the sucrose: F - 2 , ( 1 - F - 2 ) m , 1 - F - 2 , 6 - G - 1 , 2 - F - 1 , ( 2 - F - 1 ) n , 2 - F , and 4. an inulo- n -ose series without a terminal glucose F -1,(2-F-1) n ,2-F. While the first three fructan series were present in relatively high concentrations in all samples with high amounts of small fructans, the inulo- n -ose series was detectable in most samples, but in varying concentrations.

Characterization of fructan biosynthesis in big bluegrass (Poa secunda)

Summary Most cool-season grasses contain multiple types of fructans. One exception is big bluegrass (Poa secunda Presl.). When grown under specific controlled environmental conditions it synthesizes only β-2,6-linked fructans. This study analyzed fructan accumulations, enzyme activities and gene expression in big bluegrass. Detachment/illumination and cool treatments effectively induced the accumulation of fructans in leaf tissues. Enzyme assays indicated that 6-SST (sucrose : sucrose 6-fruc tosyltransferase)- and 6-SFT (sucrose : fructan 6-fructosyltransferase)-like activities were the major enzyme activities involved in fructan biosynthesis in big bluegrass leaves. A full-length cDNA of the putative 6-SFT gene was cloned using RT-PCR and RACE techniques. The deduced amino acid sequence showed 69 percnt; identity with barley 6-SFT. Homology was also high with other fructosyltransferases and some invertases. The abundance of putative 6-SFT mRNA showed a coincidence with fructan accumulation and 6-SFT activity. We suggest that 6-SFT is the major enzyme involved in fructan biosynthesis in big bluegrass but it may also exhibit limited 6-SST activity.

Carbohydrate changes in chicory (Cichorium intybus L. var. foliosum) during growth and storage

Abstract The levels of sucrose and fructose in chicory ( Cichorium intybus L. var. foliosum ) roots remain about the same over the growing season while levels of total non-structural carbohydrates (TNC) and fructans increase. At the onset of cooler fall temperatures and especially during storage, sucrose and fructose contents increase. Concurrently, a second fructan series that contains no glucose (inulo- n -ose; n = 2–18) accumulates, while at the same time, fructans (inulin) with a high degree of polymerization (DP) and TNC decrease. Chicory leaves contain low concentrations of fructans. Only trace amounts were found in the leaf lamina but leaf petioles, especially in the basal region, contained higher levels. The inulo- n -ose series up to DP 4 (inulotetraose) is also detectable in leaves.

Separation and Quantification of Fructan (Inulin) Oligomers by Anion Exchange Chromatography

ABSTRACT Accurately quantifying inulins according to their degree of polymerization (DP) has long challenged fructan researchers. This paper describes recent advances in anion exchange chromatographic separation and improved quantification of inulin oligomers up to DP 8. Pure inulin standards were prepared by fractionating water-soluble carbohydrate extracts of Jerusalem artichoke ( Helianthus tuberosus L.) tubers using gel permeation chromatography. Samples of each pure inulin oligomer were freeze-dried and used to prepare aqueous standards of known concentrations. Elution times in a Dionex anion exchange (HPAE) system run isocratically increased non-linearly with increasing DP. Separation times for polysaccharides up to DP 40 were reduced by the use of a sodium acetate gradient. Responses by the pulsed amperometric detector (PAD) per μ g of inulin decreased in a regular manner as DP increased. Inulin polysaccharides become increasingly difficult to quantify as DP increases. In spite of this limitation, high-performance anion exchange chromatography with pulsed amperometric detection provides a convenient and rapid method to separate and quantify inulins of low to moderate DP.

Fructans in crested wheatgrass leaves

Crested wheatgrass is an important cool-season grass that has become naturalized in many semiarid regions of the western U.S. It provides ground cover and reduces soil erosion caused by water and wind. Additionally, crested wheatgrass produces important forage for livestock and wildlife on 6 to 8 million hectars of western rangeland. It is well adapted to semiarid cold desert regions because of its cool temperature growth and drought tolerance. Understanding the biosynthesis of fructans in crested wheatgrass is important because of their likely role in both cool temperature growth and drought tolerance. Recent research described a major gene (6-SFT) in crested wheatgrass that is involved in fructan biosynthesis. 1-kestotriose, the major DP3 fructan in crested wheatgrass, serves as the substrate for the two major DP4 fructans, 1&6-kestotetraose and 1,1-kestotetraose. The three major DP5 fructans are 1&6,1-kestopentaose, 1,1&6-kestopentaose and 1,1,1-kestopentaose. The major DP6 fructan is 1&6, 1&6-kestohexaose. We postulate that 1&6,1&6-kestohexaose is synthesized from the addition of a fructose to 1&6, 1-kestopentaose. This paper provides structures of the various DP 3, 4, 5 and 6 fructan types produced by crested wheatgrass and provides suggested biosynthetic pathways for all major fructan linkage types present.

A quantitative histochemical procedure for measurement of starch in apple fruits

Measurements of starch (e.g. amyloplasts in stomatal guard cells, sieve elements, root tips or the starch sheath) is often very difficult using most analytical methods. An evaluation was made of interactive computer image analysis of starch measurements in apple fruits. The results obtained indicate that quantitative histochemistry can be an appropriate method to quantify starch. Correlations for starch values between the image analysis system and a colorimetric system were quantified. The thickness of plastic-embedded slices had no influence on the accuracy of the area occupied by image-quantified starch (starch/slice) or on its variance. The magnification of the objective also had no effect on measured starch-occupied areas (starch/slice), but there were big differences in variance. The number of replications required to establish statistically significant differences were calculated.