Growth and photosynthesis of photoautotrophic callus derived from protoplasts of Solanum tuberosum L.

We describe a photoautotrophic culture procedure of potato (cvs Kennebec, Haig, DTO-33) callus derived from mesophyll protoplasts. The protoplast culture was initiated at very low concentration of glucose (down to 0.25 g l(-1)). Callus was subcultured under CO2 enriched air and glucose suppressed by the successive dilutions with glucose free media. Regeneration was successfully obtained under photoautotrophic conditions. The characterization of oxygen exchange and of some enzymes and metabolites of carbon assimilation indicated that chlorophyllous callus, grown on carbohydrate free medium, developed the photosynthetic pathway typical of C3 plants. By comparing the fresh weight of callus cultivated in the light or in non-photosynthetic conditions (in darkness or in the light +3-(3,4-Dichlorophenyl)-1,1-dimethylurea) we concluded that growth depended to about 70 to 88 % on photosynthesis.