Fructan metabolism occurs in many temperate grasses when ambient temperatures are cool. Fructan is believed to influence the cold hardiness of grasses and to have osmoregulatory and carbohydrate storage functions. In the cold deserts of the western United States, crested wheatgrass (Agropyronspp.) usually maintains metabolically active leaves throughout the winter. The investigation reported here concerns nonstructural carbohydrate content of crested wheatgrass during a growing season (September-June). Fructan accumulated in plant parts during the fall and spring when temperatures were near 15°C. However, fructan content was lowest when temperatures were coldest. Surose content peaked when fructan levels were low and when maximum daily temperatures remained below 0°C. We propose that fructan biosynthesis in leaf vacuoles provides a sink for photosynthates when temperatures are too cold for translocation, and growth. Stored fructan then provide a readily available substrate for sucrose synthesis and plant growth. Because crested wheatgrass maintains green leaves during the winter and is capable of photosynthesis at temperatures near 0°C, less stored carbohydrates are required for respiratory maintenance and spring growth than for warm-season grass
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