Tree Physiology Advance Access first published online on December 3, 2008
This version published online on December 17, 2008
Tree Physiology, doi:10.1093/treephys/tpn009
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Dynamic changes in concentrations of auxin, cytokinin, ABA and selected metabolites in multiple genotypes of Douglas-fir (Pseudotsuga menziesii) during a growing season
1 Centre for Forest Biology, Department of Biology, University of Victoria, 3800 Finnerty Road, Victoria, BC V8W 3N5, Canada
2 Corresponding author (lkong{at}uvic.ca)
3 Plant Biotechnology Institute, National Research Council of Canada, 110 Gymnasium Place, Saskatoon, SK S7N 0W9, Canada
4 Western Forest Products Ltd., 8067 East Saanich Road, Saanichton, BC V8M 1K1, Canada
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Abstract |
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Changes in concentrations of several endogenous phytohormones and metabolites were analyzed in the long shoots of nine genotypes of coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) at five developmental stages: (1) closed buds, (2) flushing buds, (3) rapidly elongating shoots, (4) growing shoots and (5) near full-length shoots during one growing season. When averaged across genotypes, indole-3-acetic acid (IAA) concentration was high at stages 1 and 3. The only pattern that correlated with cone productivity was the one that was unique to IAA, in which high concentrations at stages 3 and 4 were found in all genotypes with high female cone productivity. Concentrations of isopentenyl adenosine (iPA) decreased and zeatin riboside (ZR) concentrations increased as the buds initiated and differentiated; ZR was 30 and 28 ng g–1 dry weight (DW) at stages 1 and 4, respectively, before increasing to 166 ng g–1 DW at stage 5. Isopentenyl adenosine peaked at 92 ng g–1 DW at stage 2 and declined to low concentrations at stages 4 and 5. Zeatin-O-glucoside was 30 ng g–1 DW at stage 1, declined at stages 2 and 3 and increased at stages 4 and 5. High abscisic acid (ABA) concentrations were positively correlated with rapid shoot elongation (stages 1 and 2), but as growth slowed and terminated, ABA concentrations decreased. Abscisic acid was 7 µg g–1 DW at stage 1, increased to 13 µg g–1 DW at stage 2 and then declined. The glucosyl ester (GE) of ABA decreased rapidly in early summer, and increased inversely with an increase in ABA. Between stages 1 and 2, ABA-GE decreased from 10 to 0.2 µg g–1 DW and then increased. Of the ABA catabolites studied, 7'-hydroxy-ABA was about 2 µg g–1 DW at stage 1, declined at stages 2 and 3 and increased at stages 4 and 5; phaseic acid concentrations were low at all stages, whereas dihydrophaseic acid was detected only at stages 4 and 5.
Keywords: long shoot, plant hormones
Received April 21, 2008; Accepted September 2, 2008
This version contains the full author list, including S.J. Owen.