Photoinduction of spore germination in Marchantia polymorpha L. is mediated by photosynthesis

The effects of light on spore germination (protrusion of protonemata) in the liverwort Marchantia polymorpha L. were examined. Spore germination was found to be light dependent and light irradiation for 10 h or longer was necessary. Test using specific wavelengths showed that the entire spectrum from near UV to red light was effective, red light being the most effective. Spore germination could be induced by intermittent irradiation with 15-min red light pulses given every 1 or 2 h for 24 h. The effect of intermittent red light was not reversed by subsequent or simultaneous far-red light irradiation. However, spore germination was inhibited by the photosynthesis inhibitor DCMU (100 mu M). Complete inhibition of spore germination was found when DCMU was given during the light period. When DCMU was applied during the dark periods, only a slight reduction of germination rate was observed. Further, it was found that Chi formed in the spores during imbibition in darkness. Light sensitivity increased at nearly the same rate as the appearance of Chi. Moreover, spore germination was induced in total darkness by the addition of glucose to the medium. These results clearly indicate that photosynthesis mediates the photoinduction of spore germination in Marchantia polymorpha.