Inhibition of female cone production in white spruce by red light treatment during night under field conditions

Abstract

Ten-year-old white spruce trees were evaluated for their ability to produce female cones in response to night-interrupted exposures of red light. Under field conditions, red-light treatments varied with time during the growing season, frequency of treatment within each cycle, and duration of exposure (dosage). Red light inhibited the production of female cones. No one particular combination of red-light duration, or frequency or growing season was more effective than any other. The inhibitory effect seen in 1975 preconditioned the natural 1976 induction of cones so that a reduced cone crop was observed in trees two years after light treatment. This represents the first demonstration of a negative control and carry-over of the flowering response in conifers under field conditions by specific light energies. These results suggest the possibility of new opportunities for the remote sensitization by light of specific phases of the life cycle of spruce trees.