DEVELOPMENT OF AUXIN AUTOTROPHY IN NICOTIANA-TABACUM CALLUS-CULTURES

Changes of auxin and ethylene metabolism of Nicotiana tabacum var. Xan thi callus were investigated in relation to auxin-independent growth. During the habituation process, changes occur progressively in hormone metabolism in auxin-heterotrophic tissues: the potential for the dest ruction of indoleacetic acid (IAA) increases, the IAA level in the cul tures rises slightly, and the auxin sensitivity of the callus becomes modified. Preceding the onset of habituation, ethylene production is e nhanced although the tissues retain their ability to undergo regenerat ion. Gradual changes in auxin metabolism and ethylene production confi rm the epigenetic character of the habituation process.