Cardenolides of Digitalis obscura: The effect of phosphate and manganese on growth and productivity of shoot-tip cultures

Cardenolide composition of leaves from wild and micropropagated elite plants of Digitalis obscura (genotype T4) has been investigated and no qualitative differences were found among their major cardenolides (series A). All of the detected glycosides belong to the digitoxose-type cardenolides. Genins represented less than 2% of the overall content, while lanatoside A was the predominant cardenolide (ca. 65%) in all samples. The cardenolide yield of micropropagated D. obscura plants depended on the age and development of the cultures, but productivity of long-term cultures (2 years) was quite similar to that of the parent plant. Changes in the concentrations of phosphate or manganese ions in the nutrient media did not significantly affect the biosynthetic capacity of shoot-tip cultures, which was not correlated with increases or decreases observed in growth and development of the regenerated shoots or in their contents in photosynthetic pigments. (C) 1997 Elsevier Science Ltd.