1978 Volume 46 Issue 4 Pages 495-500
The mutual effects of thermo-and photo-periodism on growth in Viburnum Awabuki K. were studied.
1. The chilling treatments (3°C) were applied in autumn and the night temperature in the greenhouse was kept at 18°C under various photoperiods after chilling treatment. When the period of chilling treatment was shorter, such as 0-30 days, growth depended strongly on photoperiod and grew vigorously under long-day and did not grow under short-day. In the case of chilling treatment of 45 days, a symptom of conversion from long-day in to short-day was recognized and grew vigorously under 12 hours of photoperiod. When the period of chilling treatment was longer, such as 60-70 days, the response of growth to short-day was vigorous.
2. When a high night temperature of 25°C was kept continuously from summer, dependence on long-day was strongest. Long-day caused continuous and vigorous growth but short-day caused periodic and poor growth. When a night temperature of 18°C was kept, long-day caused periodic growth and growth was poor and stopped for a long period under short-day.
3. The longer the photoperiod was, the more vigorous the growth was. When the night temperature was kept 18°C after a high night temperature in summer, growth stopped under all of the photoperiods in October and growth started again from March to May without chilling and growth was vigorous under long-day and was poor under short-day.
These results suggest that the response of growth to photoperiod in Viburnum Awabuki K. occurred by interdependence of thermo-periodism.
