GROWTH-RESPONSE OF FESTUCA-ALTAICA, FESTUCA-HALLII, AND FESTUCA-CAMPESTRIS TO TEMPERATURE

In Alberta, the rough fescue complex consists of Festuca altaica Trin. , Festuca hallii (Vasey) Piper, and Festuca campestris Rydb. The poten tial commercial value of these species for grazing, and their ecologic al significance, necessitates an increased understanding of their envi ronmental adaptation. This study compared the growth response of the t hree species at five temperature regimes of 7:3, 12:8, 17:13, 22:18, a nd 27:23 degrees C (light:dark; 18-h photoperiod). Seedlings were esta blished and grew for 10 weeks at 18 degrees C before being trimmed to a height of 3.5 cm and randomly assigned (36 pots of each species) to the growing environments. Growth was followed for 12 weeks. Temperatur e had a significant effect on most plant variables but the response di ffered among species. The optimal temperature for dry matter accumulat ion was 17:13 degrees C, and for tillering 12:8 to 17:13 degrees C. Fe stuca Hallii and F. campestris exhibited a faster tillering rate than F. altaica, which had the heaviest tillers and highest leaf extension rate. The root to shoot ratio declined at temperatures above 17:13 deg rees C. The significance of these observations to the geographical dis tribution of the species is discussed.