ISSN:
1365-3040
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Gomphrena macrocephala St.-Hil. (Amaranthaceae) is a perennial herb that grows spontaneously in the cerrado and is characterized by well-defined phenological phases throughout the year. Soluble carbohydrates are the main reserve compounds of the tuberous root and constitute approximately 50% of the dry weight. These sugars were partially characterized as fructans forming a single homologous series, different from inulin, the most common fructan of dicotyledons. The mean molecular weight of polysaccharides was high and reached 37 kDa in the dormant phase. Fructan spherocrystals were detected in the tuberous root after treatment with ethanol, being associated with the parenchyma of secondary xylem. The content, composition and mean molecular weight of fructans were related to phenology. In late dormancy, there was a marked increase in monosaccharides, particularly fructose, and a concomitant decline of polysaccharides, probably as a result of fructan breakdown. During sprouting and in the vegetative phase, the contents of oligosaccharides and low molecular weight polysaccharides increased. A gradual rise in the molecular weight of polysaccharides occurred during the reproductive phase and at early dormancy, concurrently with decreasing levels of oligosaccharides. The capacity of G. macrocephala to accumulate readily accessible sugars, such as fructans, instead of starch, in response to environmental changes, may be of considerable advantage, since the cerrado is often subjected to seasonal drought and burnings.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-3040.1993.tb00515.x
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