Benzylaminopurine induces phenocopies of floral meristem and organ identity mutants in wild-type Arabidopsis plants.

Arabidopsis thaliana (L.) Heynh. has been used as a model system to investigate the regulatory genes that control and coordinate the determination, differentiation and morphogenesis of the floral meristem and floral organs. We show here that benzylaminopurine (BAP), a cytokinin, influences flower development in Arabidopsis and induces partial phenocopies of known floral homeotic mutants. Application of BAP to wild-type inflorescences at three developmental stages results in: (i) increase in floral organ number; (ii) formation of abnormal floral organs and (iii) induction of secondary floral buds in the axils of sepals. These abnormalities resemble the phenotypes of mutants, clv1 (increase in organ number), ap1, ap2, ap3 (abnormal floral organs) and ap1 (secondary floral buds in the axils of first-whorl organs). In addition, BAP induces secondary floral buds in the axils of perianth members of ap2-6, ap3-1 and ag mutants, and accentuates the phenotype of the ap2-1 mutant to resemble the ap2-6 mutant. These observations suggest that exogenous BAP suppresses the normal functioning of the genes for floral meristem identity and thereby affects flower development and the later stages of floral organ differentiation.