ABSTRACT
This chapter discusses cytokinin mutants that have been induced, usually by chemical means, since no spontaneous mutants are known. Identifying screening targets is probably the most difficult component in the process of isolating cytokinin mutants. The mutants that have been isolated so far have fallen into the categories of greening phenomena, cell growth in vitro, and morphogenesis. Several groups have produced auxin and cytokinin-resistant mutants of Nicotiana plum-baginifolia in the last few years. Interestingly, several of these mutants provide evidence that screening for hormone mutants in this way can be fraught with problems. The use of Arabidopsis for molecular genetic studies on plants makes it an obvious species for the isolation of hormone mutants, including cytokinin mutants. N. W. Ashton et al. described the isolation of a number of auxin- and cytokinin-rcsistant mutants in auxotrophic backgrounds. The ove mutants are the only cytokinin mutants retrieved by total isolation without any selection pressure.
