RED LIGHT, BLUE LIGHT, AND COPPER ION IN THE PHOTOPERIODIC CONTROL OF FLOWERING IN LEMNA PERPUSILLA 6746

L. perpusilla, 6746 grown in HUTNER's medium (containing a highlevel of EDTA) responds as a short-day plant under white orred light, but is almost completely daylength-indifferent underblue. In a medium containing ca. 2µmoles/liter of unchelatedcopper ion, it flowers rapidly under all photoperiods, white,blue or red. Although certain long-day blue schedules permitflowering even on HUTNER's medium, blue is not simply "inactive"photoperiodically, since inclusion of a single brief red exposurein certain blue schedules is sufficient to prevent floweringas though the whole schedules were red. The indicated blue-redinteraction should prove important for further analyses of photoperiodismin this plant. ¹Research carried out at Brookhaven National Laboratory underthe auspices of the U.S. Atomic Energy Commission.