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Seasonal Changes in Nonstructural Carbohydrate Levels of Wheat and Oats Grown in a Semiarid Environment¹

Nonstructural carbohydrate (NSC)levels of vegetative tissues were examined in two cultivars of wheat (Triticum aestivum L.) and of oats (Avena sativa L.) to determine the seasonal distribution patterns and amounts of NSC present in these crops when grown under the dryland conditions of southwestern Saskatchewan. Ethanol (95 %) was used to extract short chain carbohydrates while oligosaccharides were extracted with water. Both fractions of carbohydrates were more prevalent in the stems than in green leaves; only low levels were found in dead leaves. The green-leaf carbohydrate levels were relatively stable throughout the growing season and did not fluctuate in response to seasonal rainfall. Carbohydrates accumulated in the stems to a maximum (25 to 48% of the dry weight) about anthesis and then declined toward maturity. Significant differences in stem carbohydrate levels were observed between wheat and oats and between cultivars within a species. Although similar trends were found in both years of this experiment, stem carbohydrate concentrations differed. The results support the concept that the stem may act as a temporary storage organ for NSC to correct a phase difference between the time of maximum photosynthate production by the plant and the time of maximum requirement for carbohydrate by the developing grain.

Key Words: Triticum aestivum L. • Avena sativa L. • Drought stress • Vegetative tissues • Ethanol extract • Water extract

² Research scientists, Research Station, Research Branch, Agric. Canada, Swift Current, Saskatchewan. S9H 3X2.

Accepted for publication September 2, 1981.