Temperature Effects on Partitioning of 14C Assimilates in Tall Fescue (Festuca arundinacea Schreb.)

Fructan synthesis and carbon partitioning to roots of tall fescue (Festuca arundinacea Schreb.) were studied with a 14C-labelling technique at three growth temperatures: 24/17 ⚬C, 16/10 ⚬C and 8/5 ⚬C (day/night). Plants at 16/10 ⚬C and 8/5 ⚬C had an increased proportion of assimilates allocated to the root system; 10 d after exposure at 14CO2, the relative carbon partitioning to the roots averaged 12.5, 16.3 and 26.8% respectively, at 24/17 ⚬C, 16/10 ⚬C and 8/5 ⚬C. Chilling temperatures induced an increase in the amounts of sucrose and fructans in leaves. Interestingly, a similar pattern occurred in roots where low-DP fructans (DP < 8) are the predominant nonstructural carbohydrate constituent. Incorporation of 14CO2 into root oligo- and polysaccharides showed a progressive movement of radioactivity from sucrose to fructans. These results show that the roots can serve as a carbon storage organ and that fructan synthesis depends on sucrose supply. The function of the fructan stored in the roots is unknown.