Photomixotrophic cultures of Marchantia polymorpha were examined under light irradiation using glucose as an organic carbon source. The activity of ribulose 1,5-bisphosphate carboxylase/oxygenase in the cells was found to be maximum at an absorbed light energy of E-C = 8.7 x 10(2) W/kg and the respiration rate of the cells remained at a low level in the range of E-C=1.7 x 10(2) to 1.5 x 10(3) W/kg. Batch culture of M. polymorpha was carried out in a bioreactor while keeping the Ec value at about 3.5 x 10(2) W/kg by regulating incident light intensity between 19 and 220 W/m(2). During the culture conducted under controlled light, CO2 evolution from the reactor was effectively suppressed and the obtained cell yield was 0.88 kg dry cells/kg glucose, whereas the yield was 0.62 kg dry cells/kg glucose throughout the culture conducted at the constant incident light intensity of 50 W/m(2).