Carbohydrate Availability and Shoot Formation in Tobacco Callus Cultures

Tobacco callus grown on a shoot‐forming medium containing sorbitol or no carbon source survived, but did not produce shoots. Transfer of tissue from a sucrose medium to carbohydrate‐deficient media and vice versa suggested that the growth of the tissue was a function of a total period in contact with available carbohydrate. Both starch and free sugars in the tissue were utilized during shoot initiation. Furthermore, it appeared that the continuous availability of carbohydrate was required for shoot primordium growth and/or their development into leafy vegetative shoots in dark‐grown cultures.