title: Dynamic changes in concentrations of auxin, cytokinin, ABA and selected metabolites in multiple genotypes of Douglas-fir (Pseudotsuga menziesii) during a growing season.
abstract: 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 microg g(-1) DW at stage 1, increased to 13 microg 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 microg g(-1) DW and then increased. Of the ABA catabolites studied, 7'-hydroxy-ABA was about 2 microg 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.
authors.affiliation: Centre for Forest Biology, Department of Biology, University of Victoria, 3800 Finnerty Road, Victoria, BC V8W 3N5, Canada. lkong@uvic.ca
authors.forename: Lisheng
authors.initials: L
authors.lastname: Kong
authors.forename: Suzanne R
authors.initials: SR
authors.lastname: Abrams
authors.forename: Stacey J
authors.initials: SJ
authors.lastname: Owen
authors.forename: Annette
authors.initials: A
authors.lastname: Van Niejenhuis
authors.forename: Patrick
authors.initials: P
authors.lastname: Von Aderkas
mesh_terms: D000040:Abscisic Acid / Q000235:genetics / Q000378:metabolism*; D003583:Cytokinins / Q000235:genetics / Q000378:metabolism*; D014644:Genetic Variation; D005838:Genotype; D007210:Indoleacetic Acids / Q000378:metabolism*; D018519:Meristem; D010937:Plant Growth Regulators / Q000235:genetics / Q000378:metabolism*; D018520:Plant Shoots; D028224:Pseudotsuga / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D014197:Trees / Q000254:growth & development / Q000378:metabolism
chemical_list: D003583:Cytokinins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D000040:Abscisic Acid