A Plant Scientist Was Hired by a Greenhouse Operator to Devise

Multiple Choice

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 a long-day (short-night) plant. Which of the following treatments has the best chance of creating iris blooms in winter?

A) artificially increase the period of darkness in the greenhouse
B) increase the temperature to more closely follow summer temperatures
C) alternate 4 hours of darkness with 4 hours of light repeatedly over each 24-hour period
D) interrupt the long winter nights with a brief period of light