Organdifferenzierung und Glykosidbildung bei in vitro kultivierten Blattexplantaten von Digitalis purpurea L; Einfluß verschiedener Wuchsstoffe, Nährlösungen und Lichtverhältnisse

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In explants of Digitalis purpurea leaves the action of growth regulators on callus growth, organ formation and cardenolide synthesis is investigated. The compounds used are: indole acetic acid (IAA); naphthyl acetic acid (NAA); 2,4 dichlorphenoxy acetic acid (2,4 D); kinetin; gibberellinic acid A3 (GA3); applied in concentrations ranging from 10 -7 g/ml to 5 · 10 -5 g/ml. Cultivation was carried out in basal media according to Heller and to Murashige and Skoog (114 & S1/2) under, dif f er.ent conditions oif illumination. Auxin (IAA or NAA 10 -6 g/ml) induces root differentiation in leaf explant; this effect is more enhanced by cultivation in Heller's medium under high light intensity than in M & S1/2 medium under less intense illumination or in the dark. The root formation induced by IAA is altered under the addition of kinetin or GA3; root growth is inhibited and root formation is steadily replaced by other forms of differentiation. In the explants cultured in M & S1/2 medium the inhibitory effect of the two growth substances is strongly pronounced. Besides root inhibition two further effects are observed with kinetin, being absent in Helper's medium but remarkable in M & S'/2 medium (a) differentiation of buds due to higher concentrations -of kinetin; (b) with increasing concentrations of the cytokinin a shift of the activity zones from the upper portions of the leaf fragments, lying outside the medium, towards the lower portions, touched by the medium. This activity-shift can be recognized by regression of root formation in the upper regions and furtherance in the lower regions. The bud formation occurs preferably in the fragments near the border contacting the medium. GA3 applied singly or together with IAA leads to striking callus formation. 2,4D leads to root anomalies and the callus assumes a friable consistency. In the newly formed tissue the existence of cardenolides is demonstrable, however ito a lesser extent than in leaf tissue of Digitalis purpurea . The amounts of cardiac gylcosides produced in the root and callus tissue under the influence of IAA are not essentially altered by the simultaneous presence of kinetin or 2,41) to IAA. GA3 exerts an inhibitory effect on the synthesis of glycosides. From these experiments can be concluded that light influences the action which auxin exerts on glycoside formation in newly emerged roots of leaf explants. The tissue responds to a decrease of light intensity with a decrease of glycoside synthesis.