The Photocontrol of Spore Germination in the Fern Ceratopteris richardii

This paper describes how different wavelengths of light regulate spore germination in the fern Ceratopteris richardii</it>. This species does not exhibit any dark germination. Maximum photosensitivity of the spores is reached 7 to 10 d after imbibition. An increase in the red light fluence above the threshold fluence of 1016 quanta.m−2 leads to a corresponding increase in germination. In sequential irradiation experiments, farred light can reverse this red light-mediated germination to the level observed with the far-red light control. Blue light fluences above 1020 quanta.m−2 can also block the germination response to red light. Moreover, this antagonistic effect of blue light is not reversed by subsequent irradiation with red light. It is therefore concluded that phytochrome and a distinct blue light photoreceptor control C. richardii</it> spore germination. These interpretations are entirely consistent with the published literature on other fern genera.