The promotion of flowering in forest trees by gibberellin [formula omitted] and cultural treatments: A review of the possible mechanisms

• Published in: Forest ecology and management Vol. 19; no. 1; pp. 65 - 84
• Main Authors: Pharis, Richard P., Webber, Joe E., Ross, Steven D.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.1987
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/0378-1127(87)90012-0

Research papers noting success with gibberellin A 4 7 ( GA 4 7 ) on 19 species representing five genera of Pinaceae family conifers are reviewed. Evidence is presented which suggests that exogenous GA 4 7 plays a direct morphogenic role in the promotion of flowering in these conifers that is independent of nutrient diversion or effects on the vigor and mitotic activity of potentially reproductive primordia. Various cultural treatments (e.g. water stress, root-pruning, girdling, nitrate-N-fertilization and N starvation) which promote flowering, often synergistically with GA 4 7 , can slow the oxidative metabolism of applied GA's and can also result in a build-up of endogenous less-polar GA's (such as GA 4 7 ). This suggest that exogenous GA 4 7 probably promotes flowering in a manner analogous to the natural promotion of flowering. Just how GA's act to promote flowering remains obscure. However, the evidence supports a hypothesis that GA's, endogenous and exogenously applied, are used preferentially for vegetative growth processes, with increased flowering occurring only after a threshold concentration of effector GA is reached.