Skip to Main Content
Hormonal control of second flushing in Douglas-fir shoots.Author(s): Morris Cline; Mark Yoders; Dipti Desai; Constance Harrington; William Carlson
Source: Tree Physiology. 26: 1369-1375
Publication Series: Scientific Journal (JRNL)
PDF: View PDF (760 KB)
DescriptionSpring-flushing, over-wintered buds of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) produce new buds that may follow various developmental pathways. These include second flushing in early summer or dormancy before flushing during the following spring. Second flushing usually entails an initial release of apical dominance as some of the current-season upper lateral buds grow out. Four hypotheses concerning control of current bud outgrowth in spring-flushing shoots were tested: (1) apically derived auxin in the terminal spring-flushing shoot suppresses lateral bud outgrowth (second flushing): (2) cytokinin (0.5 mM benzyladenine) spray treatments given midway through the spring flush period induce bud formation: (3) similar cytokinin spray treatments induce the outgrowth of existing current lateral buds; and (4) defoliation of the terminal spring-flushing shoot promotes second flushing. Hypothesis 1 was supported by data demonstrating that decapitation-released apical dominance was completely restored by treatment with exogenous auxin (22.5 or 45 mM naphthalene acetic acid) (Thimann-Skoog test). Hypothesis 2 was marginally supported by a small, but significant increase in bud number; and Hypothesis 3 was strongly supported by a large increase in the number of outgrowing buds following cytokinin applications. Defoliation produced similar results to cytokinin application. We conclude that auxin and cytokinin play important repressive and promotive roles, respectively, in the control of second flushing in the terminal spring-flushing Douglas-fir shoot.
- You may send email to email@example.com to request a hard copy of this publication.
- (Please specify exactly which publication you are requesting and your mailing address.)
- We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
CitationCline, Morris; Yoders, Mark; Desai, Dipti; Harrington, Constance; Carlson, William. 2006. Hormonal control of second flushing in Douglas-fir shoots. Tree Physiology. 26: 1369-1375
Keywordsapical dominance, auxin, branching, cytokinin, defoliation, lateral and terminal bud outgrowth, spring flushing, terminal shoot
- The possible roles of nutrient deprivation and auxin repression in apical control
- Apical dominance and apical control in multiple flushing of temperate woody species.
- Mapping of quantitative trait loci controlling adaptive traits in coastal Douglas-fir. I. Timing of vegetative bud flush.
XML: View XML