THE INFLUENCE OF THE RATIO OF INCANDESCENT TO FLUORESCENT LIGHT ON THE FLOWERING RESPONSE OF MARQUIS WHEAT GROWN UNDER CONTROLLED CONDITIONS

Abstract

When Marquis wheat is grown under artificial conditions, the main light energy (lamp watts) supplied by fluorescent light should be supplemented by at least 35 per cent of incandescent light in order to have a photoperiodic effect close to the maximal. Increasing the percentage up to 100 per cent resulted in slightly earlier flowering. This effect of incandescent light was caused, not by earlier floral initiation, but by an increase in the rate of stem elongation and a hastening of the later stages of floral differentiation. This action of incandescent light could not be replaced by substituting pink fluorescent for one-third of the white fluorescent lights.To obtain a photoperiodic effect equal to that of high light energy from combined fluorescent and incandescent bulbs, it is recommended that the daylength be extended by sufficient incandescent light to give an intensity of at least 50 ft.-c. at plant level.