title: The Effect of Periodic Dark Interruptions in Long Photoperiods on Floral Induction in the Long-Day Plants Silene armeria L., annual Lunaria annua L. and Samolus parviflorus Raf.
abstract: After a basic fluorescent and incandescent illumination, a period of incandescent illumination was interrupted by 3 hours of darkness at different times, the total light period always being 16 h. After these Day Interruption (DI) treatments of various durations the plants were transferred to long day (LD) or continuous light (CL), where the numbers of days of flower-bud visibility were recorded. Compared with the uninterrupted controls, the DI-treatments generally accelerated flower formation to an extent which varied rhythmically with the moment in the photoperiod at which the DI was given. By involving the days to flower-bud visibility in LD or CL of originally vegetative plants in the evaluation of the results, the DI-effects could be explained as the reflection of rhythmically returning changes in the light requirement for flower formation in the course of the photoperiod. Relatively rapid flower formation after a certain DI treatment reflected a relatively low light requirement, and vice versa. Calculations of the inductive efficiencies of interrupted regions, defined as their inductive effect as percentages of the effect of LD or CL, confirmed this viewpoint. The rhythmic courses of the light requirement during the photoperiod could be distinguished as two types:
authors.affiliation: Department of Horticulture, Agricultural University, P.O.B. 30, NL 6700 AA Wageningen, The Netherlands, Publication 510.
authors.forename: S J
authors.initials: SJ
authors.lastname: Wellensiek