Abstract
Cell suspension cultures of Paul's Scarlet rose were grown over a 14-day period, during which a 50-fold increase in fresh weight occurred. Three phases could be recognized from weight, DNA determinations, and microscopic examination. From days 0 to 7, cell division was accompanied by cell expansion; from days 7 to 10, only cell expansion occurred; and from days 10 to 14, there was no further growth.
When acetate-1-14C was supplied continuously to 4-day and 12-day cells, 14C was readily incorporated into lipid, CO2, organic acids, amino acids, and protein. In the older cells, relatively greater amounts of 14C were recovered in organic and amino acids, and accumulation of 14C in these components continued after a steady rate of incorporation of 14C into protein and 14CO2 had been established.
Glutamate-14C was the most heavily labeled compound recovered after a pulse of acetate-1-14C in both cell types and was depleted when acetate-1-14C was removed, particularly rapidly in 4-day cells. 14C was rapidly lost from the malate-14C labeled during the pulse of acetate-1-14C in 4-day cells, whereas malate-14C continued to increase in 12-day cells after the pulse. Glutamate-14C was shown to be the source of the 14C accumulating in malate in 12-day cells.
Several other soluble amino acids were labeled during a pulse of acetate-14C in both cell types. After the pulse most of the 14C lost from these was recovered in the corresponding amino acid in protein, showing that only protein precursor pools had been labeled. The behavior of asparagine was exceptional since its 14C content increased after the pulse and no turnover was apparent. The kinetics of labeling of aspartate, malate, and CO2 showed that oxaloacetate generated in the tricarboxylic acid cycle following the pulse was not in equilibrium with aspartate.
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