Changes in levels of endogenous plant hormones in cambial regions of stems ofLarix kaempferi at the onset of cambial activity in springtime

Abstract

The total amounts of endogenous indole-3-acetic acid (IAA), cytokinins, and abscisic acid (ABA) were quantified by gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) in cambial regions of the main stems ofLarix kaempferi during the spring season. During the sampling period, cambium in the dormant state entered the active meristematic state. The total amount of IAA did not change at the onset of cambial reactivation but increased when the active division of cambial cells became apparent. Four cytokinins —trans- andcis-ribosylzeatin (RZ),N6-isopentenyladenine (iP),N6-isopentenyladenosine (iPA) — were quantified, but no zeatin (Z) was detected. The total amount of the four cytokinins together and the total amount of isopentenyl-type cytokinins (iP and iPA) varied during the sampling period but did not appear to be specifically associated with cambial activity. The total amounts oftrans- andcis-RZ remained relatively constant during the sampling period, as did the total amount of ABA. The results suggest that there is little correlation between total amounts of endogenous plant hormones in the cambial region and reactivation of the cambium during the spring.