Akira Kato

Energetics of tobacco cells, Nicotiana tabacum L., growing on sucrose medium

SummaryBatch cultures of tobacco cells induced from Nicotiana tabacum L. cv. Bright Yellow-2 were carried out under oxygen-limited conditions using sucrose as the sole carbon source. Maintenance coefficients for sugar, m, and for oxygen, mO, were 0.02 mmol glucose/g cell dry weight/h and 0.09 mmol O2/g cell dry weight/h, and true growth yields for sugar, YG, and for oxygen, YGO, were 107 g cell dry weight/mol glucose and 61 g cell dry weight/mol O2, respectively.Balance equations based on electrons available from the culture suggested that the carbon-substrate consumed by the cells might be metabolized mainly in biosynthetic processes without the excretion of extracellular products.

Relationships Between Nucleic Acid, Nitrogen, and Growth Rate of Tobacco Cells in Suspension Culture

SummaryChanges in the amount of nucleic acid and nitrogen, and the relationships between these amounts and the growth rate of tobacco cells (Nicotiana tabacum L. cv. Bright Yellow-2) at different initial nitrogen concentrations in the medium, were examined in batch cultures. During culture in basal medium, the amount of intracellular nucleic acid expressed per unit of dry biomass was 36.3 mg RNA g−1 cell and 8.1 mg DNA g−1 cell at the beginning of batch culture. These values increased 2.5 fold for RNA and 1.5 fold for DNA during the exponential growth phase and then gradually decreased with the decline in the growth rate. Similar changes were also observed in the medium containing less nitrogen. The specific growth rate, μ (day−1), of the culture corresponded to the magnitude of the intracellular RNA content (mg RNA g−1 cell), and the linear relationship, RNA=38μ+23 was obtained. In addition, there were remarkable positive correlations between the total and protein nitrogen, and μ during the cultures. The mononucleotide composition of total RNA (AMP+UMP)/(GMP+CMP) which was suggested to be a convenient index of metabolic activity was nearly constant (0.78 to 0.80) during tobacco cell culture in the basal medium.