Abstract
This paper analyzed time-course changes in concentrations of gibberellins, abscisic acid (ABA),
and indoleacetic acid (IAA) from bud tips and xylem sap of Calocedrus formosana trees that had
been treated with gibberellin A3 (GA3). GA3 was applied to the branches of good flowering clone
no. 11 and poor flowering clone no. 22 of C. formosana trees at the Tashueshan seed orchard in
March, April, and May, and then bud tips were collected every 7~10 d. In addition, the same clones
(nos. 11 and 22) at the Liukuei seed orchard that flower naturally were selected as controls. The GA1
and GA3 contents of bud tips from the 2 clones at the Tashueshan and Liukuei seed orchards were
quantified and showed no significant differences; the GA1 and GA3 contents were about 1.3~18.6 ng
(g.dry weight)-1. After treatment with GA3 at the Tashueshan seed orchard, GA1 and GA3 contents
in bud tips rapidly increased until the floral buds had differentiated, and then the contents were reduced
1/2~1/10-fold to 10~800 ng (g.DW)-1. Nevertheless, GA1 and GA3 contents in bud tips from
the Liukuei seed orchard (control without GA3 treatment) were all < 10 ng (g.DW)-1. In conclusion,
gibberellins could induce flowering of C. formosana, but there was no relationship between gibberellins
and floral bud initiation. The ABA content in bud tips rapidly decreased during the bud collection
period and had dropped 1/5~1/50-fold during floral bud initiation. The IAA content in bud
tips suddenly appeared during floral bud initiation, and the concentration was 32~143 ng (g.DW)-1,
but the IAA content was almost zero after floral bud initiation. We speculated that IAA was possibly
involved in floral-bud initiation. Furthermore, the xylem sap in shoots was collected for analysis of
GAs after treatment with GA3. At 1 wk after treatment, large amounts of GA1, GA4, and GA9 were
found in the xylem sap, but there was no GA3. Three weeks later, contents of GA1 and GA4 were
still detected in the GA3 treatment and control groups, but GA9 was not found. Therefore, GA9 may
play a transport role from branches to buds, and then GA9 is converted to GA1 and GA4.