Fructan and total carbohydrate accumulation in leaves of two cultivars of timothy (Phleum pratenseVega and Climax) as affected by temperature

Fructans are thought to have a role in physiological responses and growth under low temperatures in cool-season grasses. Two cultivars of timothy (Phleum pratense), Vega, a Scandinavian cultivar, and Climax, introduced from England and currently grown in the U.S., were compared in relation to their response to different growth temperatures. Leaf blades of neither of the two cultivars accumulated any fructan of high degree of polymerisation (DP) in leaves when grown at constant day/night temperature of 20 °C. At temperatures lower than 20 °C, content of total carbohydrate increased, especially in Vega. At 10/5 °C (day/night), a pronounced accumulation of total carbohydrate and high DP fructans occurred. A pronounced accumulation occurred also when plants grown at 20 °C were transferred to 10 °C for several days before sampling. A decrease in temperature is thought to induce a temporary imbalance in source and sink activities. Accumulated fructan was in the 12-80 DP range. Only very small amounts of low DP oligosaccharides (DP 4-12) were detected. The two timothy cultivars showed no apparent qualitative difference in fructan accumulation. Generally, Vega had significantly higher total carbohydrate and fructan content than Climax, suggesting possible differences in genetic adaptation to cool growth temperatures.