A Comparison of the Effects of Long Days and Exogenous Growth Regulators on Growth and Flowering in Strawberry,<i>Fragaria χ Ananassa</i>Duch.

Abstract

SummaryApplications of GA3, 2-NOA or CEPA, made at different times during a six-week period of natural short days in autumn, decreased the numbers of flowers produced in the following spring; where flowers developed, the number of achenes on the primary fruits was always reduced. Long days (LD) also decreased the numbers of flowers and achenes per fruit, but in the timing of their effects none of the growth regulators exactly imitated photoperiod. GA3 application in spring after floral initiation was completed also caused changes similar to those induced by LD (increases in petiole length, number of stolons, leaf area and the rate of production of open flowers). The responses to LD increased with longer duration of light given as a night-break. Even in continuous light there was a further response to GA3. For stem elongation and flower growth, the greatest response to GA3 occurred in continuous light, indicating that one effect of long photoperiods is to increase sensitivity to exogenous gibberellins.