Cytokinin contents and specific characteristics of tissue strains from three sexual genotypes of Mercurialis annua : Evidence for sex-gene involvement at callus-tissue level.

Analyses of the endogenous cytokinin contents of established tissue strains of Mercurialis annua are reported. The strains were derived from three individuals (strong male, weak male, female), differing by one of the three genes determining sex. The data are compared with the endogenous cytokinins of male and female shoot apices. Tissue strains are characterized by the disappearance of natural cytokinin metabolites in the female; in both males, Δ(2)-isopentenyl-adenosine and only trans-ribosylzeatin exist but in different quantities. Benzyladenine and ribosylbenzyladenine were identified in the three strains but the quantities also differed as a function of the genotype. The marked differences in cytokinin metabolism of tissue strains indicate that sex genes continue to function in the dedifferentiated state. Each strain also exhibited persistent morphological and histological characteristics, and a different sensitivity to the withdrawal of 2-4-dichlorophenoxyacetic acid or benzyladenine from the medium. Each had a specific and characteristic effect on the organogenesis of nodes cultivated in close proximity to callus pieces. These data complement the above results and show that sex genes act at the callus-tissue level. The possibility that these genes act at the early stages of embryogenesis of male and female individuals is also discussed.