Factors Affecting Growth and Aggregate Dissociation in Batch Suspension Cultures of Datura innoxia (Miller)

Growth kinetics of Datura innoxia batch suspension cultureswen monitored by a Klett-turbidimetric technique. While cultured. wt varied linearly with Klett units, f. wt and packed cellvolume did not. Turbidimetrically determined doubling timeswere highly reproducible. The method proved to be useful inthe determination of acutely lethal conantrations of a seriesof anti-metabolites. In certain circumstances, aggregate dissociation in batch suspensioncultures of D. innoxia was found to be coupled to growth rate.Suspensions maintained with 10^–5 M 2,4-D exhibited a relativelyslow growth rate with a high degree of aggregate dissociation:10^–4 M 2,4-D promoted a maximum growth rate, but dramaticallysuppressed aggregate dissociation. At 10^–5 M 2,4-D, themitotic index of smaller-aggregate fractions was greater thanthe mitotic index of the large-aggregate fraction. At 10^–5M 2,4-D the converse was observed. Supraoptimal 2,4-D concentrationsthus enhanced both aggregate dissociation and the growth ofsmaller aggregates. When present in concentrations promoting optimal growth. malicand succinic acids caused a decrease in aggregate dissociation.Casein hydrolysate dramatically enhanced growth, but did notaffect aggregate dissociation to the same degree as 2,4-D orthe Krebs cycle organic acids. Suggestions are made concerningmedium composition to be used in future mutant selection schemesusing D. innoxia. Datura innoxia (Miller), suspension culture, growth kinetics, mitotic index, 2,4-dichorophenoxy acetic acid