Limitation of tobacco callus tissue growth by carbohydrate availability.

Growth rate, maximum dry weight yield, and carbohydrate utilization were measured with pith callus derived from Nicotiana tabacum L. var. Wisconsin No. 38. Maximum tissue dry weights increased as carbohydrate (either glucose or sucrose) in the medium was increased. The time at which maximum growth was obtained coincided with the time at which carbohydrate was exhausted from the medium. The addition of carbohydrate to the medium before the end of log phase growth supported that amount of additional growth which would have been obtained if all of the carbohydrate had been added to the medium prior to planting the tissue. Maximum obtainable dry weights at logarithmic growth rates greater than 0.16 doubling per day depended on the amount of carbohydrate in the medium and not on a particular hormonal regime.