Abstract:
Effects of temperature and growth stage on
vegetative bud development and stem hardiness of red-osier
dogwood during winter dormancy were investigated.
Results were related to a degree growth stage model and
were used to develop models to predict growth stages, to
quantify development, and to predict hardiness.
Maximum rest development was promoted by 5°-20°C
with increasing rate with decreasing temperature.
Developmental rates changed throughout this phase.
Chilling temperatures to deepen rest were effective from
vegetative maturity. Model predicted maximum rest by two
days in both years and daily developmental status.
In the decreasing rest phase, development was
promoted by 5°-15°C with increasing rate with decreasing
temperature. No development occurred at 20°C.
Developmental rates changed throughout this phase.
Chilling temperatures to decrease rest were effective
from maximum rest. Model predicted end of rest by three
days in both years and daily developmental status.
In the quiescent phase, development was promoted by
5°-20°C with increasing rate with both increasing
temperature and developmental stage. Model predicted
spring bud break within three days for both years.
Accuracy in predicting daily developmental status varied
between years.
Decreasing temperatures promoted increasing
acclimation. Acclimation rates at 5°-20°C increased from
vegetative maturity and were highest at maximum rest. In
the decreasing rest phase, 7°-20°C caused deacc1imation.
Early in the quiescent phase only 5°C promoted
acclimation; later, all temperatures caused
deacc1imation. Accuracy of models in predicting
hardiness varied among developmental phases and between
years with average deviations of 1.8° to 4.7°C.
