The continuous culture of plant cells.

Steady states of growth were established in continuous culture, both as chemostats and turbidostats, using a cell suspension of Acer pseudoplatanus L. Stable states were maintained over a wide range of dilution rates in chemostat cultures. The relationships between stead-state biomass, the concentration of nitrate (the limiting nutrient) and dilution rate were generally that to be expected from chemostat theory although the yield coefficient was not a constant. The size, composition and physiological state of Acer cells depended upon growth rate. There was no significant alteration in the basic growth processes of Acer cells transferred from batch to continuous cultures. The growth of Acer cells in chemostats was not entirely predictable. Furthermore, the specific growth rate of batch cultures of Acer cells was found to vary (mean doubling time = 70 hours; minimum = 20 hours). The rate of cell division in batch cultures of Acer cells was increased by increasing the initial concentration of 2,4-dichlorophenoxyacetic acid. Cell division in batch cultures of Acer was readily synchronised by a simple starvation and regrowth treatment. It was possible to follow the growth of cultures through up to five synchronous cell generations, with an average 85% participation at each cytokinesis. Some basic markers in the cell cycle of Acer cells were established and model cell cycles constructed. DNA synthesis was restricted to a period of ca. 15 hours. G2 was relatively constant at ca. 16 hours. Nuclear division (1-2 hours) was separated from cell division by a 10-hour lag. G1 was most variable (13-37 hours) producing variation in cell-cycle times coincident with that of specific growth rate in random cultures. S-phase or its initiation was coincident with other periodic, metabolic events.