Lighting for Plant Growth, p. 197 (1972)
Elwood D. Bickford, Stuart Dunn

Dormancy usually can be broken by a chilling period, long photoperiods, or a chilling period followed by long days. Downs and Borthwick (1956) found that long days (16 hour) produced continuous growth of several tree seedlings including catalpa (Catalpa bignonioides and C. speciosa), elm (Ulmus americana), birch (Betula mandshurica), dogwood (Cornus florida), and red maple (Acer rubrum) as shown in Fig. 13.7. They found that Paulownia (P. tomentosa), sweet gum (Liquidambar styraciflua), and horse chestnut (Aesculus hippocastanum) did not grow continuously but eventually became dormant under the growing conditions. Intermittent growth (alternation of flushes of growth with bud formation) is exhibited by several species. Downs and Borthwick also found that the growth of pine species (Pinus taeda, P. virginiana, and P. sylvestris) was intermittent on a 16 hour photoperiod and continuous on a 14 hour photoperiod. Oak (Quercus sp.) is also known to exhibit an intermittent growth pattern under long days or continuous lighting. Under continuous lighting Q. rubur produced eight successive flushes in one season. (Wareing, 1956).

Continuous lighting biblio