5,6-Dichlorobenzimidazole-1-beta-D-riboside, specific inhibitor of cytokinin activity in tobacco cell suspension cultures.

Tobacco cell suspension cultures were supplemented with 4 to 10 microM 5,6-dichloro-1-beta-D-ribofuranosyl-benzimidazole (DBR). The cell suspensions were cultured in the presence or without a cytokinin, kinetin (N6-furfuryladenine). The responses of the cultures to DRB and (or) kinetin were measured by the evolution of cell mass or cell counts in the cultures, as a function of time or kinetin concentration. Chlorophyll biosynthesis was also used as a test-response to cytokinin and (or) DRB activities. It was concluded that DRB behaves as a specific inhibitor of the physiological responses to cytokinins. The evolution of the inhibition ratio versus kinetin concentration shows that DRB is not a competitor of the cytokinins.