Phytohormones and their metabolites during long shoot development in Douglas-fir following cone induction by gibberellin injection

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 GA(4) and GA(7), including small amounts of GA(3) and GA(1), was stem-injected into each tree in amounts of 0, 4, 40 or 400 mg. One week after injection, concentrations of GA(4), GA(7) and GA(3) were elevated in all GA-treated samples. The ratio of GA, to GA7 decreased significantly at Week 3. Absolute concentrations of all gibberellins declined sharply at Week 3 alter GA application. After 5 weeks, GA, and GA., 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 m, 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 stern dry mass in Week 5. Seed orchard data revealed that injection of either 40 or 400 rug GA enhanced female cone formation, whereas male cone formation was enhanced only by 400 rig 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.