A comparison of British and North African varieties of tall fescue (Festuca arundinacea). 3. Effects of light, temperature and day length on relative growth rate and its components.
Shading of plants grown outdoors decreased RGR and NAR but increased leaf. area ratio; values for the N. African Syn I and Syn II were similar to those for S170. When plants were transferred from outdoors to controlled environment in Jan., all 3 parameters were greater in Syn I and Syn II at 5° day/-3°C night, but not at 18°/-3°C. In freshly germinated seedlings transferred to 5°/-3°C, RGR, NAR and leaf-area ratio were again least in S170, but in 15°/5°C and 10°/0°C the varieties differed only slightly in leaf-area ratio and RGR. In all varieties NAR was less at 10°/0°C than at 15°/5°C, and in S170, NAR was less at 5°/-3°C than at 10°/0°C. During the 1963.4 winter, the above 3 parameters were greater in Syn II than in S170 during a period of particularly low temp., both in natural winter day. length and in 16.h days. In controlled environment at 5°/-3°C these parameters were again greater in Syn II in both long and short days. At these low temperatures there was some indication of a slight varietal difference in response to daylength. Results suggested that temp, was the main environmental factor controlling the seasonal differences in growth between S170 and N. African material.-R.B.