Factors Influencing Morphogenesis in Excised Roots and Suspension Cultures of Atropa belladonna

Excised root cultures of Atropa belladonna L. and A. belladonna var. lutea Döll, established from liquid-grown seedlings and from callus, when allowed to continue growth without subculture for several weeks, spontaneously initiate shoot buds from small nodules of callus which arise at the cut ends of the roots. The frequency and rapidity of formation of such buds is dependent upon the number of passages through which the roots have been subcultured. The morphogenetic expression of callus cultures and of suspension cultures derived from them is influenced not only by the time that the root cultures have been maintained in culture but by the composition of the medium used for callus initiation and subsequent culture. The presence of elevated levels of ammonium ions in these media favours the development of incipient plants rather than roots. Cultures have thus been obtained in which the predominant form of morphogenesis is embryogenesis (as established in a subsequent paper by Konar, Thomas, and Street, 1972).