Identification and Quantification of Cytokinins in the Xylem Sap of Mistletoes and Their Hosts in Relation to Leaf Mimicry

Abstract

Cytokinins present in the xylem saps of two species of Amyema mistletoes and three species of Eucalyptus hosts have been measured using radioimmunoassays employing antibodies elicited against zeatin riboside, dihydrozeatin riboside and isopentenyladenosine. The radioimmunoassays, when used in combination with enzymatic treatments and chromatographic separation techniques, allowed the detection of a wide variety of cytokinin bases, ribosides, O-glucosides and nucleotides. Column chromatography over paraffin-coated silica gel was used to separate cytokinins from contaminating polar plant compounds. Results demonstrated a closer relationship between the types and concentrations of cytokinins in the xylem saps of mistletoes and their hosts in a mimicking situation (A. miquelii on E. polyanthemos) than in a non-mimicking situation (A. pendulum on E. cinerea).