Determination of hit numbers from dose-response curves for phytochrome control of seed germination (Lactuca sativa cv Noran)

The dose-response curves for the induction of thermo-dormant (pretreated at 37 °C) Lactuca seeds and of far-red dormant (pretreated by long exposure to far-red light) Lactuca seeds by red light show a difference in shape. From the shape of the curves it is calculated that for initiation of germination in thermo-dormant seeds at least 2 quanta (2 = 660 nm) must be absorbed per active unit, in far-red dormant seeds at least 7 quanta.