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.
Seasonal dynamics of non-structural carbohydrates in bulbs and shoots of the geophyte Galanthus nivalis.
Seasonal dynamics of non-structural carbohydrates were studied in Galanthus nivalis L. over a 2-year period. The plants were collected in the field and separated into above- and below-ground biomass. The polysaccharide fraction of the bulbs consisted of fructans and starch. Seasonal variations suggest that the polysaccharides were utilized for carbon and energy supply for re-growth and flower development. With the re-sprouting of the bulbs in autumn the fructans within the bulbs were depolymerized and an increase of low degree of polymerization fructans as well as sucrose was observable. Within shoots the major polysaccharides were fructans, the starch content was much lower. Gas liquid chromatography and high-performance, anion-exchange chromatographyanalysis of the fructan fraction revealed that the fructans within the shoots were predominantly those with a low degree of polymerization. In addition to the two polysaccharides the other dominant sugar in shoots was sucrose. During the period of slow re-growth and flowering, fructan and starch pools were depleted to different degrees. Calculation of the difference between the carbohydrate content at the start of visible growth and at the time of lowest content revealed that the starch pool showed a higher depletion than the fructan pool. During the re-growth periods in 1996/97 and 1997/98 fructans were catabolized by 39 and 32% only, whereas the starch pool was depleted by 92% (1996/97) and 79% (1997/98), respectively. During rapid shoot growth and fruiting, the bulbs and above-ground organs appeared to be competing sinks for the photosynthetically fixed carbon. Refilling of the bulbs carbohydrate reserve started in February/March In shoots, the period of refilling the bulbs was characterized by a low content of oligosaccarides and a high content of hexoses.
Concentration of amino acids in wine after the end of fermentation by Saccharomyces cerevisiae strains
Both quantitative and qualitative differences in the utilization and release of assimilable nitrogen by two wine strains of Saccharomyces cerevisiae (cerevisiae and capensis) under different conditions of oxygen were observed. These differences were influenced by the presence of oxygen at the beginning of the fermentation, and by the strain of S cerevisiae. The release of some amino acids post-fermentation may be the result of reoxidation of NAD(P)H in order to maintain a normal redox balance. Copyright © 2003 Society of Chemical Industry