Seasonal changes in levels of cytokinin-like compounds from Douglas-fir xylem extrudate

High-performance liquid chromatography, immunochromatography, and radioimmunoassay were used to identify cytokinin-like bases and glycosides in xylem sap of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Isopentenyladenosine-type (isopentenyladenine and isopentenyladenosine) and zeatin-riboside type (zeatin, zeatin riboside, and dihydrozeatin riboside) cytokinins were detected during springtime. A glucosyl conjugate of zeatin riboside was also present in small amounts. Levels of cytokinin-like compounds varied throughout the spring but were generally highest in late April to early May.