Photoreversibility of Flower Initiation.

Open Access
Publisher Website
Google Scholar
Abstract
The reversible photoreaction previously shown to control the germination of light-sensitive seeds and the flowering of cocklebur (Xanthium pennsylvanicum.) was extended to two short-day plants, Biloxi soybean (Glycine max) and pigweed (Amaranthus caudatus), and two long-day ones, Wintex barley (Hordeum vulgare) and Hyoscyamus niger with detailed study of cocklebur and Biloxi soybean. Measurement of the treatment stimulus on Xanthium was based on 8 stages of the development of the staminate inflorescence and on soybean on the number of nodes bearing flower primordia. The action of red energy was reversible by far red several times during a brief period near the middle of the inductive dark period. However, the degree of re-promotion by far red decreased with each successive red-far-red cycle until finally no re-promotion could be attained. Long exposures to far red were less effective than exposures of 2 to 5 minutes. Far-red re-promotion of flowering was reduced as the duration of darkness between the red and the far-red irradiations was increased. Finally, when 30 to 45 minutes of darkness intervened between the two kinds of radiation, no re-promotion could be attained. The effect of this intervening period of darkness was nullified by reducing the temperature during that period. It is suggested that the far-red-absorbing form of the pigment is the biologically active form and causes a slow build-up of a condition inhibitory to flowering.