Calcium restriction induces cardenolide accumulation in cell suspension cultures of Digitalis thapsi L.

The removal of calcium ions from Murashige and Skoog culture medium induced a marked increase in the accumulation of cardenolides in cell suspension cultures of Digitalis thapsi. Cell viability was not affected although growth was slightly reduced. Strontium ions could substitute for calcium in inhibiting cardenolide production, this effect of calcium being reversed by the addition of LaCl3 or ethyleneglycol-bis-(β-aminoethyl ether)-N,N'-tetraacetic acid. The results suggest that calcium, apart from its general effects on growth, may play a role in the regulation of cardenolide metabolism in a concentration dependent manner.