Abstract

The embryogenetic responseof culturedDaucus carota L. ‘Queen Anne's Lace’ callus was employed to attempt fractionation and identification of a repressive factor produced byCitrus medica L. ovules. The factor was evidently synthesized and released into the medium continuously, inasmuch as citron ovules that had been autoclaved with the medium were completely infeffective. The inhibition could be attributed to volatile and nonvolatile components. A substantial part of the inhibition was prevented by continuously refereshing the atmosphere within the cultures with filtered air. Monitoring of the gases produced by citron ovule sections under conditions simulating bioassays disclosed significant evolution of carbon dioxide, ethylene and ethanol. Repression of embryogenesis was not averted by trapping the liberated ethylene. On the other hand, ethanol in concentrations equivalent to those released by citron ovules suppressed asexual embryogenesis dramatically. The adverse effect of ethanol was reversed immeditaley upon transfer to ethanol-free medium. Another investigation had disclosed anti-embryogenetic effects of auxin, abscisic acid and gibberellin. Analysis ofCitrus ovules excised from young fuits disclosed those of monoembryonic citron to contain concentrations of IAA, ABA and GA3 several times higher than those of polyembryonic Ponkan mandrain. The nonvolatile protion might be identified with these hormonal substances.

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