Tryptophan and indole-3-acetic acid accumulation in Acer cell cultures and its relationship with cell autolysis.

The accumulation and decline of 'free indole-3-acetic acid (IAA)' and tryptophan has been monitored in cells of Acer pseudoplatanus L. grown in batch suspension cultures. The period of maximal IAA accumulation per cell or per unit dry weight of tissue was found to precede the peak of tryptophan accumulation by several days. A study of cell viability throughout a growth passage indicated the presence of a basal level of non-viable cells of 5-7%, with only minor increases occurring during the first week of the three-week growth passage. The results suggest that IAA biosynthesis is not regulated by substrate availability arising from proteolysis in dead cells.