1970 Volume 39 Issue 2 Pages 144-148
The effect of light-break on the sex differentiation in cucumber has been investigated using the variety “Higan-fushinari.” Red light induced more female flower nodes than either one of white, green, blue and far-red lights did. The light-breaks with red light of very low intensity could induce more female flower nodes in plants as compared with the control which has grown up without interruption of the dark period. The higher the intensity became, the more the female flower nodes occurred. One minute interruption with red light induced more female flower nodes than the not interrupted. The number of female flower nodes increased with prolonging the duration of light-break. The female increasing effect with red light was reversed by the subsequent far-red light. This effect was quite reversible, alternatively. The divided light-break induced much more female flower nodes than a single continuous one, having the same total energy, did. These results will safely show that the sex differentiation in cucumbers may be controlled by the mechanism concerning the phytochrome.