The results of rheological measurements on 10 different plant cell suspension 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 result of elongated cell morphology. The rheology of Papaver somniferum (poppy) cell suspensions is quite different; poppy suspensions behave as 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 attributed to a lack of elongation in batch-grown poppy cells. A simple correlation 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 that 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, further confirming the dependence of rheology on plant cell morphology. The rheology of a wide variety of other plant suspensions at 200 g FW/L is presented. Most cell suspensions, including soybean, cotton, bindweed, 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 cultures. This demonstrates that complex rheology associated with elongated cell morphology is much less common than low-viscosity Newtonian behavior. High viscosity in plant cell culture is therefore not an intrinsic characteristic of plant cells but, instead, is a result of the ability to grow cultures to extremely high cell densities due to low biological oxygen demand.

Thermal diffusion measurements have been made on a series of solutions of polystyrene as follows: (1) Five molecular weights (10 000 to 336 000) in toluene; (2) 136 000 molecular weight in o-xylene, styrene, ethyl benzene, dioxane, and pyridine; (3) Styrene dimer in toluene and styrene; measurements were also made on some binary monomeric mixtures. The thermodynamic property X∂μ/∂X describes adequately the concentration dependence of the thermal diffusion ratio α. It appears that that portion of the motion of the polystyrene molecule in dilute and somewhat concentrated solutions which is segmental involves 10—13 chain atoms in the moving segment. The results seem consistent with Kauzmann and Eyring's picture for motion of long chain molecules.

No abstract

In examining the growth kinetics of cell suspensions of opium poppy (Papaver somniferum), the increase in biomass with time was observed to be linear over the entire batch growth period of up to 20 days. Although batch growth profiles were reproducible utilizing the same inoculum, growth rates varied tremendously when experiments were inoculated with cells from different flasks. Both of these phenomena are difficult to explain with conventional batch growth models. In a series of a experiments, phosphate was determined to be the growth-rate-limiting substrate. By expressing growth rate in terms of the intracellular reserves of phosphorus, a growth model which expresses kinetics in terms of the intracellular phosphorus contents of the cells is shown to predict both linear growth character and inoculum dependent variability in growth. The stationary phase phosphate content of seven plant suspension cultures of different plant species was found to be comparable to phosphorus levels of phosphate-starved poppy cells, which suggests that phosphate limitation may be common for plant tissue culture. The applicability of this model to other biological systems which display similar batch growth patterns when subjected to inorganic nutrient deprivation is discussed.

A solution is presented to the boundary value problem for the transient development of the velocity profile in a viscoelastic fluid subjected to the sudden onset of shearing in an idealized viscometer. A differential Oldroyd type of constitutive equation is used to describe the mechanical behavior of the fluid. The results indicate that the elastic nature of the fluid significantly increases the length of time required for the steady-state velocity profile to be established. A solution is also presented for the drainage of a viscoelastic fluid off a vertical plate. The predicted initial elastic overshoot or rapid drainage of the fluid is in qualitative agreement with reported experimental results.