ABSTRACT
This chapter begins with cytokinin habituation and related phenomena that occur during normal and neoplastic development. It deals with the nature of the heritable change, then turns to genetic, developmental, and physiological factors influencing habituation, and discusses the proposal of molecular mechanisms that can account for both the stability and reversibility of the habituation process. The average degree of habituation of the subclones was approximately equal to the value obtained with the parent clone, indicating that there is no cell selection during cloning and, hence, that the frequency of clones reflects the cellular constitution of the tissues. Rapid habituation in culture appears to reflect types of stable changes that also occur during normal development in the plant. Cells derived from tissues in different parts of the plant can differ both in their cytokinin requirement and their tendency for habituation. Deficiencies in plastid function appear to be causally related to habituation.
