A green‐pigmented callus of the moss, Sphagnum imbricatum Hornsch. ex. Russ., was induced and a chlorophyllous cell suspension culture was established using a modified Murashige and Skoog's medium without plant hormones. Cell growth in the light in the presence of glucose started after a short lag and was exponential for 12 days. The chlorophyll level was about 15 μg (mg cell dry weight)−1 and photosynthetic activity ca 20 to 50 μmol O2 (mg chlorophyll)−1h−1. Cell growth in the light was negligible in the absence of glucose under ordinary air, but photoautotrophic growth was possible under elevated CO2 concentrations. In the dark, the moss cells grew heterotrophically and continued to synthesize chlorophyll, although at a much reduced rate. The suspension‐cultured cells redifferentiated protonemata and shoots when transferred to solid Knop's medium. In contrast to the callus cells, which could not assimilate nitrate, redifferentiated plantlets could use nitrate as the sole nitrogen source.

Chlorophyllous cells in suspension culture from the moss, Barbula unguculata Hedw., grown under photoheterotrophic conditions were transferred to photoautotrophic conditions. The cells started to grow photoautotrophically without selection. Maximum growth was observed under irradiances of more than 5 W m2 and in an atmosphere enriched with 1% (v/v) CO2. Under optimum growth conditions, dry weight and chlorophyll content in the culture had increased 20‐fold after 20 days of cell growth. High concentration of chlorophyll [10–20 μg (mg dry weight)−1] and high photosynthetic actively [30–70 μmol O2 evolved (mg chlorophyll)−1 h−1] were observed throughout the culture period. In sugar‐free culture medium, cell growth did not occur in the dark or in the presence of 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) under light, although cell growth was observed in glucose‐containing medium under those conditions. When cells that were grown photoautotrophically for one year were transferred to glucose‐containing medium under ordinary air, they started to grow heterotrophically both in the light and in the dark.

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