Cytokinins: 7-glucosylation is not a prerequisite of the expression of their biological activity.

(14)C-labelled benzyladenine-7-glucoside (0.57 μM) supplied to cytokinin-requiring Nicotiana tabacum (cv. Wisconsin 38) cells cultivated in liquid medium was slowly absorbed and resulted in rather large intracellular quantities of benzyladenine-7-glucoside (30 pmol/10(5) cells) but did not show any biological activity, while 0.01 μM benzyladenosine induced cell division. In this case the resulting intracellular quantity of benzyladenine-7-glucoside formed was 3.3 pmol/10(5) cells. Also, N(6)-(Δ(2)-isopentenyl)adenosine induced cell division in these tobacco suspensions without being significantly 7-glucosylated. These data provide strong evidence that the 7-glucosylation of cytokinins is not a prerequisite of the expression of their biological activity.