A plant scientist was hired by a greenhouse operator to devise a way to force iris plants to bloom in the short days of winter.
Iris normally blooms as long-day (short-night) plants. Which of the following has the best chance of creating iris blooms in winter?A) Increase the temperature to more closely follow summer temperatures.B) Artificially increase the period of darkness in the greenhouse.C) Alternate four hours of darkness with four hours of light repeatedly over each 24-hour period.D) Interrupt the long winter nights with a brief period of light.
Interrupt the long winter nights with a brief period of light.
Explanation:
Long day plants, also called short night plants, flower when the dark period is equal or less than the critical period specific for the species. These plants normally flower in summers when nights are short and days are longer. Winters have a long dark period and do not support flowering in shirt night plants.
A continuous dark period is critical for flowering. A short night plant can flower in winters (having longer dark periods) if the dark period is interrupted by exposing the plant with a flash of light. To make short night plants, such as iris to flower in winters, the plant should be given short period of light after completion of critical dark period.
