Studies on the Light Controlling Flower Initiation of Pharbitis Nil

VIII. Light-Sensitivity of the Inductive Dark Process

Abstract

An inductive dark period of 16 hours was divided into 4 phases consisting of 4hours each.
1) Light-sensitivity of these 4 phases was investigated. The first phase was most stable to the light, the light-stability of the 2nd, 4th and 3rd phases decreasing in the order mentioned. The first phase proceeded to some extent under daylight fluorescent light of 2000lux, but the 3rd phase did not proceed under light of 10lux.
2) Light-stability of the 1st phase was not influenced by the light-intensity preceding it.
3) Spectral sensitivity of the inductive dark process varied with the phase.
During the 1st and 2nd phases, far-red radiant energy was more effective than red. During the 3rd and 4th phases, red was more effective than far-red. In the first phase, blue was less effective than violet, but the reverse was the case in the
other three phases. In all phases, blue and violet were less effective than red or far-red.