Effects of Auxin and Phenobarbital on Morphogenesis and Production of Digitoxin in Digitalis Callus |
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Authors: | Palazon, Javier Bonfill, Mercedes Cusido, Rosa M. Pinol, M.T. Morales, Carmen |
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Affiliation: | Laboratori de Fisiologia Vegetal, Facultat de Farmacia, Universitat de Barcelona AVD/Diagonal 643, 08028 Barcelona, Spain |
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Abstract: | Pieces of callus obtained from seedlings of Digitalis purpureawere grown on solid Murashige-Skoog's medium supplemented with1 mg liter1 BA and 0.1 mg liter1 IAA or NAA, withor without phenobarbital (40 mg liter1). The replacementof the natural auxin IAA by the synthetic auxin NAA increasedcallus growth and inhibited organogenesis, whereas the additionof phenobarbital had the opposite effect. Morphometric measurementsrevealed a high ratio of vacuole to cytoplasm (v/v) in calluscells. This ratio was affected by the different treatments inthe same way as the fresh weight. The activity of mitochondrialcytochrome P450scc (the enzyme that provides the precursor,pregnenolone, for the biosynthesis of cardenolide in foxgloveplants) was detected in the relevant fraction of callus grownunder all experimental conditions, and its activity was increasedby the addition of phenobarbital. The different treatments testedincreased the cardenolide content and quantifiable amounts ofdigitoxin were detected in all callus tissues. It is of specialinterest that phenobarbital added to the culture medium increasedthe accumulation of digitoxin. The mechanism affecting the developmentand production of cardenolide in callus tissues of D. purpureaby phenobarbital and the replacement of IAA by NAA is discussed. (Received July 18, 1994; Accepted December 14, 1994) |
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