| Abstract: | The responses of steady-state cell populations of Acer pseudoplatanusL. (sycamore) in chemo-stats to changes in the nitrate concentrationof their environment was generally predictable by equationsderived for ideal, free-cell, nitrate-limited populations. Astep-down in nitrate concentration in the input medium of achemostat produced interlocking oscillations in spent-mediumnitrate, intracellular pools of nitrate and amino-N, proteinaccumulation, and cell division. The rate of nitrate uptakeinto the cell and thus the flow of nitrogen into protein (andultimately the specific growth rate) was seen to be finely regulatedby spent-medium nitrate concentration. Steady states of growth of sycamore cells were established withglucose as the limiting nutrient both from inoculation and afterswitching from nitrate to glucose limitation. Glucose-limitedcells produced by glucose step-down of a nitrate-limited populationsuffered major losses of cell material, including starch andcell wall polysaccharide, to the extent that protein then accountedfor c. 70% of cell dry weight. |
