Thermo-dormant lettuce seeds can be induced to germinate by small doses of far-red light. The dose-effect curve appears to be an optimum curve. After having been irradiated with a supra-optimal inhibiting dose of far-red the seeds can be reinduced by red light, the threshold red dose for induction being now 104 times as large as it is without the far-red preirradiation. It is concluded that the inductive effect of far-red light is mediated by an uncommon form of phytochrome which is considered to be also present in etiolated Avena seedlings and Sinapis seedlings, and in cells of Mougeotia.

Acta botanica neerlandica

CC BY 3.0 NL ("Naamsvermelding")

Koninklijke Nederlandse Botanische Vereniging

G. Blaauw-Jansen, & O.H. Blaauw. (1976). Further evidence for the existence of two phytochrome systems from two distinct effects of far-red light on lettuce seed germination. Acta botanica neerlandica, 25(3), 213–219.