Phytohormones and their metabolites during long shoot development in Douglas-fir following cone induction by gibberellin injection
Lisheng Kong (1, 2), Suzanne R. Abrams (3), Stacey J. Owen (3), Hilary Graham (4) and Patrick von Aderkas (1)
1. Centre for Forest Biology, Department of Biology, University of Victoria, 3800 Finnerty Road, Victoria, BC V8W 3N5, Canada / 2. Corresponding author () / 3. Plant Biotechnology Institute, National Research Council of Canada, 110 Gymnasium Place, Saskatoon, SK S7N 0W9, Canada / 4. Pacific Regeneration Technologies Inc., 668 St. Anne Road, Armstrong, BC V0E 1B5, Canada / Received January 11, 2008; accepted April 21, 2008; published online July 1, 2008
Summary
Changes in plant hormones and metabolites in long-shoot stems of interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) during cone induction by gibberellic acid (GA) treatment were analyzed by high performance liquid chromatography–electrospray
ionization tandem mass spectrometry in multiple reaction monitoring mode. A mixture of GA4 and GA7, including small amounts of GA3 and GA1, was stem-injected into each tree in amounts of 0, 4, 40 or 400 mg. One week after injection, concentrations of GA4, GA7 and GA3 were elevated in all GA-treated samples. The ratio of GA4 to GA7 decreased significantly at Week 3. Absolute concentrations of all gibberellins declined sharply at Week 3 after GA application.
After 5 weeks, GA1 and GA4 were below detection limits in all samples, and GA7 and GA3 were found only in the samples from trees treated with 40 or 400 mg of GA. Endogenous indole-3-acetic acid (IAA) concentrations
increased following GA injection, and peaked at Week 2 or Week 3 in the trees treated with 40 or 400 mg GA, respectively.
Injection of 400 mg of GA brought about a twofold increase in IAA concentration compared with control values. Injection of
40 and 400 mg of GA caused significant increases in stem dry mass in Week 5. Seed orchard data revealed that injection of
either 40 or 400 mg GA enhanced female cone formation, whereas male cone formation was enhanced only by 400 mg GA. Slight
decreases in concentrations of abscisic acid (ABA) and isopentenyl adenosine were observed after GA application. No significant
changes were detected in the concentrations of ABA metabolites except for a slight decrease in the concentration of 7′-hydroxy
ABA. The concentration of ABA declined during the growing season and the concentration of ABA glucose ester increased correspondingly.
