Hastening effect of intercalated long days on short-day induction in Impatiens balsamina, a qualitative short day plant.

The inductive effect of short-day (SD) cycles on floral-bud initiation in Impatiens balsamina was enhanced and the minimum requirement for SD cycles for flowering reduced by intercalated long days (LDs). Thus, floral buds developed into flowers with only 4 SD cycles in plants receiving them individually or in pairs alternating with LDs, but failed to develop in those receiving 4 SD sycles consecutively. The number of flowering plants increased while the periods to floral-bud initiation and flowering, calculated from the day of completion of 4 and 8 SD cycles, respectively, decreased with an increase in the number of intercalated LDs.