BLUE LIGHT, PHYTOCHROME AND THE FLOWERING OF LEMNA PERPUSILLA 6746

Lemna perpusilla 6746 was grown on HUTNER'S medium with sucroseunder light schedules combining red, blue and far-red light.As shown earlier, brief red exposures added to a continuousblue schedule inhibit flowering although either schedule alonepermits it; hence red and blue act together in establishinga long day (flower inhibiting) condition. However, the red exposurerequired to inhibit flowering is greater with high intensitythan with low intensity continuous blue, suggesting in additiona blue-red antagonism. Blue light reverses the effects of abrief red exposure closing a blue or far-red main photoperiod,but it also reverses the effects of a brief far-red exposureclosing a red photoperiod. Thus, blue can act either like redor like far-red, depending on the situation. All effects ofblue light on the flowering of L. perpusilla 6746 are consistentwith the notion that it establishes a Pfr level intermediatebetween those established by red and far-red light; the postulationof an additional photoreaction to explain the effects of blueseems unnecessary. ¹Research carried out at Brookhaven National Laboratory underthe auspices of the U. S. Atomic Energy Commission.