Transition from photomixotrophic to photoautotrophic growth of Asparagus officinalis in suspension culture

The literature on photoautotrophic plant tissue cultures is reviewed and results from experiments reported in which calli of Asparagus officinalis leaves were obtained on Nitsch medium and later transferred to and maintained on Murashige and Skoog medium with 1 mg/litre naphthalene acetic acid and 0·1 mg/litre kinetin. Friable, green calli were selected and replicated to obtain fine chlorophyllous, heterotrophic suspensions of individual cells and small cell aggregates. The carbon source for the suspension was 20 g/litre lactose. Four of these photomixotrophic suspensions were grown in the presence of light and in an atmosphere enriched with 1% CO2. By progressively reducing the lactose concentration continuously or discontinuously over a period of 2–8 weeks, we were able to obtain photoautotrophic growth. The transition from photomixotrophy to photoautotrophy was followed by measuring the oxygen evolution in the presence and absence of light (photosynthesis/respiration estimations). By using continuous culture and by modifying the dilution rate of the culture, we were able to obtain a photoautotrophic strain of A. officinalis with a doubling time of 7 days.