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In suspension cultured cells of Nicotiana tabacum L. cv. Wisconsin 38 the .concentration of 18 nucleotides and 3 nucleosides have been determined using a new procedure developed for the extraction, purification and HPLC separation of these compounds from plant tissue. The different nucleotide pools increase in size immediately at the onset of the batch culture and reach distinct maxima at the very beginning of the proliferative phase. The main component are the uracil nucleotides with UDP‐sugars as the predominant fraction followed by the adenine nucleotides; the energy charge is maintained at a high and constant value throughout the whole culture time. During the growth interval the increases in the nucleotide pools reveal that the cell proliferation phase is followed by an extensive phase of cell elongation. Whereas the concentration of the total nucleotides varies by a factor of about 3 along the growth curve, the ratio of uracil to adenine nucleotides is kept fairly constant indicating regulatory mechanisms for correlation of the individual nucleotide pools.

The content of the different ribonucleotides, nucleoside diphosphate sugars, NAD+ and NADP+ was determined in the leaves and roots of single plants of Nicotiana tabacum L. cv. Samsun using a new procedure. The determination makes use of extraction with HClO4 followed by extract purification and separation by a combination of anion‐exchange and reversed phase high performance liquid chromatography. The largest pools were the adenine nucleotides and the uracil nucleotides with nucleoside diphosphate sugars as the main fraction. Leaf senescence was accompanied by a strong reduction of the nucleotide content of the leaves, but the adenine nucleotide‐derived energy charge remained at a high level and even increased at the later stages of senescence. This indicates a balanced metabolism also in the older leaves and excludes the possibility that leaf senescence is triggered by the energy charge.

The concentrations of 17 nucleotides and three nucleosides have been determined in a batch suspension culture of Datura innoxia using a new procedure for extraction, purification and high-performance liquid chromatography separation of these compounds. The nucleotide pools change appreciably in the different phases of growth. These changes indicate the preparation for and initiation of cell proliferation, and reflect metabolic events during cell division, cell elongation and starvation. The main components of the nucleotide pool are uracil nucleotides, with uridine 5'-diphosphate sugars as the predominant fraction, and the adenine nucleotides. Although their concentrations vary by a factor of more than 6 the ratio of the uracil to adenine nucleotides is kept fairly constant during growth. The energy charge is maintained at a rather high value. The correlation of these events with nutrient uptake and macromolecular synthesis by the batch culture is presented in the following paper.