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

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Abstract
Growth kinetics of Datura innoxia batch suspension cultures wen monitored by a Klett-turbidimetric technique. While culture d. wt varied linearly with Klett units, f. wt and packed cell volume did not. Turbidimetrically determined doubling times were highly reproducible. The method proved to be useful in the determination of acutely lethal conantrations of a series of anti-metabolites. In certain circumstances, aggregate dissociation in batch suspension cultures of D. innoxia was found to be coupled to growth rate. Suspensions maintained with 10−5 M 2,4-D exhibited a relatively slow growth rate with a high degree of aggregate dissociation: 10−4 M 2,4-D promoted a maximum growth rate, but dramatically suppressed aggregate dissociation. At 10−5 M 2,4-D, the mitotic index of smaller-aggregate fractions was greater than the mitotic index of the large-aggregate fraction. At 10−5 M 2,4-D the converse was observed. Supraoptimal 2,4-D concentrations thus enhanced both aggregate dissociation and the growth of smaller aggregates. When present in concentrations promoting optimal growth. malic and succinic acids caused a decrease in aggregate dissociation. Casein hydrolysate dramatically enhanced growth, but did not affect aggregate dissociation to the same degree as 2,4-D or the Krebs cycle organic acids. Suggestions are made concerning medium composition to be used in future mutant selection schemes using D. innoxia.