Phytotron Analysis of a Photoperiodic Response in a High Arctic Plant Species

High arctic plants of Saxifraga rivularis require nearly continuous (23 or more h/day) irradiance of @? 0.3 ly/min for induction of floral development in growth chambers. A daily dark period of several hours' duration, or a daily low intensity irradiance period of @? 0.1 ly/min, of similar duration prevents flowering. A series of phytotron experiments showed that the plants produce preformed flower buds under a nonflowering light regime, and that the development of these buds is arrested at a developmental stage corresponding to that of the overwintering flower bud observed in the field. Approximately 7-9 days of continuous irradiance of 0.3 ly/min induces these preformed buds to flower. Both the spectral distribution of radiant energy and the total radiant flux density appear to be involved in the induction of floral development in the growth chambers.