CELL SPECIALIZATION AND CARDIAC GLYCOSIDE FORMATION IN CELL CULTURES OF DIGITALIS SPECIES

Cardenolide contents in unorganized callus and suspension cultures were low (about 0.5 – 2 ng/mg dry wt.). Though optimum experimental conditions for triggering organized growth of emerged as well as of submerged cultures varied with the Digitalis species used and the origin of the in vitro culture (leaf, stem, anther, hypocotyl) morphogenesis proceeded in all cases from callus to microglobuli with tracheidal elements, to rooted globuli or embryoids and, in some cases, to embryos and plantlets. The morphogenetic capacity was best in cultures of D. lutea, D. mertonensis and a special embryogenic strain of D. lanata obtained from anther tissue (V-strain). Under a 12 hours light-dark regime microglobuli, embryoids, embryos and plantlets turned green. Cardenolide contents in emerged cultures increased during formation of green globuli (to about 80 – 100 ng/mg dry wt. in D. lanata and D. grandiflora) whereas induction of root formation was less effective. The decisive influence of light was also observed in submerged cultures of the D. lanata V-strain. About 100 ng digitoxin equivalents/ mg dry wt. (= 2 – 3 ug/ml culture) were found in light treated cultures compared to 2 ng in the dark control.

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