The trivalent ion of a rare earth element, lanthanum, was tested for elicitor-like
effects on taxol production in suspension cultures of four different Taxus spp cells.
In T. yunnanensis cell cultures, the lanthanum ion at concentrations from 1.15 to
23.0 microM stimulated taxol production. The lanthanum ion also promoted taxol excretion
by the T. yunnanensis cells considerably. The maximum stimulation of taxol production
was achieved by the addition of 5.8 microM La3+ to the culture during mid-log growth
phase, increasing the volumetric taxol yield by nearly threefold, from 2.61+/-0.37
to 9.89+/-1.92 mg l(-1) over a 28 day culture period. At higher concentrations, i.e.
23.1 and 46.2 microM, however, the lanthanum ion caused significant growth inhibition.
For the other three Taxus cell lines, namely an embryo and a leave cell of T. chinensis
and a stem cell of T. chinensis marv, the addition of lanthanum ion to the culture
only had a significant effect on taxol production by the T. chinensis marv stem cells,
increasing the volumetric yield by about threefold to 4.69+/-0.76 mg l(-1). These
results suggest that lanthanum has elicitor-like effects on secondary metabolite synthesis
of plant cell cultures.