THE RELATIVE EFFECTIVENESS OF STANDARD COOL WHITE FLUORESCENT AND INCANDESCENT LIGHT IN THE PHOTOPERIODIC RESPONSE OF MARQUIS WHEAT, GARNET WHEAT AND WINTEX BARLEY

Abstract

It has been shown that incandescent light is about four times as effective in promoting floral differentiation in Marquis and Garnet wheat and Wintex barley, as standard cool white fluorescent light of the same foot-candle intensity, when given as an interruption in the middle of the dark period of an 8-hour day length. There is little difference in the photoperiodic effect of incandescent or fluorescent light if an equal input wattage is given to an equal area of bench space at the same distance from the lamps. Interruptions of the dark period led to an earlier change from the vegetative to the flowering condition, and interruptions continued past this change further accelerated floral development. Garnet wheat showed a greater response to long photo-periods than either Marquis wheat or Wintex barley.