Inhibition of Somatic Embryogenesis in Orchardgrass by Endogenous Cytokinins

Endogenous indoleacetic acid (IAA) and cytokinin concentrations were measured by high performance liquid chromatography in leaf sections of an orchardgrass (Dactylis glomerata L.) genotype which exhibited a high capacity for somatic embryogenesis in vitro and in two genotypes that did not exhibit this capacity. The nonembryogenic genotypes contained 3- to 4-fold higher concentrations of zeatin, zeatin riboside, dihydrozeatin, dihydrozeatin riboside, and total cytokinins than the embryogenic genotype. There were no significant differences in IAA concentrations between genotypes. Cytokinin concentrations between basal and distal sections of embryogenic genotype were not different, but the IAA concentration was significantly greater in basal sections. Somatic embryogenesis was inhibited in the embryogenic genotype by 0.001 micromolar exogenously added zeatin.