PLANT-CELL SUSPENSION-CULTURE RHEOLOGY

The results of rheological measurements on 10 different plant cell sus pension cultures are presented. Nicotiana tabacum (tobacco) suspension cultures grown in serial batch subculture display high viscosity and power law rheology. This ''undesirable'' rheology is shown to be a res ult of elongated cell morphology. The rheology of Papaver somniferum ( poppy) cell suspensions is quite different; poppy suspensions behave a s Newtonian fluids and have relatively low viscosity (less than 15 cP) at fresh cell densities up to 250 g/L. This flow behavior can be attr ibuted to a lack of elongation in batch-grown poppy cells. A simple co rrelation for the viscosity as a function of cell density is developed for poppy suspensions up to 300 g fresh weight (FW)/L. It is shown th at tobacco cells do not elongate when grown in semicontinuous culture (daily media replacement). These semicontinuously cultured cells have rheological behavior that is indistinguishable from that of poppy, fur ther confirming the dependence of rheology on plant cell morphology. T he rheology of a wide variety of other plant suspensions at 200 g FW/L is presented. Most cell suspensions, including soybean, cotton, bindw eed, and potato, display low viscosities similar to poppy suspensions. Only carrot and atriplex exhibit slight pseudoplastic behavior which corresponded to a slight degree of cellular elongation for these cultu res. This demonstrates that complex rheology associated with elongated cell morphology is much less common than low-viscosity Newtonian beha vior. High viscosity in plant cell culture is therefore not an intrins ic characteristic of plant cells but, instead, is a result of the abil ity to grow cultures to extremely high cell densities due to low biolo gical oxygen demand. (C) 1993 John Wiley & Sons, Inc.