Hormone levels in the cambial region of intact Picea abies during the onset of cambial activity

Microdialysis probes were used to sample the cambial region of Picea abies stems during the cambial reactivation period. The concentrations of ethylene and zeatinriboside in each sample were measured by gas chromatography and enzyme‐linked immuno‐sorbent assay, respectively. The ethylene level increased throughout the experimental period, except for a temporary decrease that occurred about the time of budburst on the lower branches. The zeatin‐riboside level changed relatively little during the same period. The results indicate that increased activity in the cambial region was associated with an increase in the level of ethylene but not of zeatinriboside.