Differentiation

In many callus and suspension culture systems it has been found that the cells do not produce the secondary metabolites found in the mother plant. However, when differentiation takes place, either shoot/root organogenesis or somatic embryogenesis, the differentiated tissues start producing the same secondary metabolites as the mother plant.

Thapsia garganica:Thapsigargins, calicum-ATP'ase inhibitors,
are produced in the intact plant, but not in callus culture.
Roots, shoots and somatic embryos regenerated
from the callus produce thapsigargins.

Reasons for the lack of secondary metabolite production in cell culture could be:

diversion of common precursors into primary metabolism
suppressed or reduced expression of key enzymes
lack of appropriate storage sites, such as secretory cells, cavities or sacs, latex tissue or glandular hairs that only occur in differentiated tissues.