Effect of Light Quality on the Rhythmic Flowering Response of Biloxi Soybean

The effect of red and( far-red irriclation on the plhotoperiodic behavior of plants has been the subject of intensive investigations during the past 15 years. Borthwick and Hendricks (1) have repeatedly slhown that red light, given (luring the (lark perio(l to a short-day plant, is inhibitory to flowering. This inhibition of flowering may be reverse(l in Xanthium and Biloxi soybean, by an exposure to far-red radiation given shortly after the exposure to red light (1,2). The pigment involved in these changes has been obtained in a partially purifie(d state an(l given the name phytochronme (6). The investigations relating phytochrome to photoperio(lisnm have been conducted with plants that were subjected to 24-hour cycles. Investigations with Biloxi soybean subjected to cycles longer thani 24 hours have demonstrate(d the participation of an endlogenous rhythm in its photoperiodic behavior (4. 9). The studies reported here are an attemiipt to determine the extent of the particip)ation of phytochrome in the basic en(logenious rhythmn of flowering in Biloxi soybean.