Canadian Forest Service Publications

The effect of photoperiod on vegetative growth and generative development in coniferous tree species. 1970. Roche, L. Congr. Int. Union For. Res. Organ., Sect. 22, Proceedings: International Union of Forestry Research Organizations. Finland. s.n., S.l. 8 p.

Year: 1970

Issued by: Laurentian Forestry Centre

Catalog ID: 15921

Language: English

Availability: PDF (download)

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In assessing the effect of photoperiod on the vegetative growth and generative cycle of coniferous trees a distinction is made between dormancy release and flushing, and between cessation of shoot elongation and true winter dormancy. It is suggested that under natural conditions temperature is the most important environmental factor influencing dormancy release and flushing and that cessation of shoot elongation with the formation of a terminal bud, which is closely linked to the onset of the generative cycle, is under the control of photoperiod. The view, therefore, that all theories and concepts of flowering are theories and concepts of photoperiodism could equally apply to coniferous tree species. Both dormancy, and dormancy release are discussed in relation to the microevolution of the species. It is suggested that because cessation of shoot elongation is closely linked with the onset of the generative cycle, and because of the temperature conditions prevailing in the fall, the photoperiodic control of growth cessation conifers a survival advantage on the species. A similar survival advantage is not conferred on the species by the photoperiodic control of dormancy release and flushing. The period during which there is gradual cessation of shoot elongation with the formation of a terminal bud is synchronized with the period during which primordia are most plastic in regard to their future development. There is marked meristematic activity during the period prior to true winter dormancy, and it is suggested that at this time substance are synthesized which mediate the onset of the generative cycle. It is during this period, therefore, that treatment could have maximum effect on the development of reproductive buds. In any study designed the influence the periodicity of cone crops it is necessary to distinguish between initiation of reproductive buds and their development and maturation. Factors which may influence initiation may have no effect on development and maturation and vice versa. It is possible that for many coniferous species cone crop periodicity is more closely related to development and maturation rather than to initiation of reproductive buds.