Sprouting of the fructan- and starch-storing geophyte Lachenalia minima: Effects on carbohydrate and water content within the bulbs.
The carbohydrate pool within the bulbs of Lachenalia minima W.F. Barker (Hyacinthaceae) consists of similar amounts of fructans and starch. This study was conducted to examine the changes within the pool of non-structural carbohydrates that occur during sprouting under field conditions. The bulbs were watered over a period of 23 days to simulate the onset of the rainy season. Even though there was no significant change of the total fructan content, the distribution and the composition of the fructan fraction within the different leaf scales of the bulbs altered during sprouting. The major changes occurred in the innermost scales, the total fructan content increased from 300 (day 0) to 607 (day 23) g kg-1 dry mass and high-performance anion-exchange chromatography analysis revealed a significant increase of fructans with low degree of polymerization (DP). With respect to starch, the most pronounced difference accompanying the transition to growth was also in the innermost scales. In contrast to fructans, starch content decreased from 241 (day 0) to 60 (day 14) g kg-1 dry mass. These results demonstrate that starch, and not fructan, is used as the carbon and energy source for sprouting. The water content data suggest the involvement of fructans in water relations. The preferential accumulation of low DP fructans and sucrose within the innermost scales directs the water flow to where it is most needed for growth. Similar changes were obtained for bulbs in the dry soil, but transformation rates were much slower and occurred to a lesser extent, indicating that these reactions were not triggered but were accelerated by water.
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.
Separation of plant betaines and their sulphur analogues by cation-exchange high-performance liquid chromatography
Abstract Recent interest in stress-induced accumulation of glycinebetaine in plants has stimulated the search for improved methods of assaying betaines. A method based on high-performance liquid chromatographic separation on a strong cation-exchange material combined with low-wavelength ultraviolet absorbance detection is described. This forms the basis of a rapid assay procedure for glycinebetaine using plant saps as the starting material and avoiding the need for derivatization.