Question

One set of a plant was grown at 12 hours a day and 12 hours a night period cycles and it flowered. While in the other set, night phase was interrupted by flash of light and it did not flower. Under which one of the following categories will you place this plant?

• A. Short-day
• B. Long-day
• C. Darkness-neutral
• D. Day-neutral

Answer 1

The correct option is A Short-day

On the basis of the response of plants to photoperiodism, plants are classified as day-neutral plants. These are the ones which flower regardless of the length of the period of light it is exposed to, e.g., rice, corn, and the cucumber.
Long-day plants are the plants that flower when the length of the day is more than the critical light period.
Short-day plants are the plants that flower only when the length of the day is less than or about 12 hours.

All spring flowering plants are short day plants, such as Chrysanthemum, poinsettia and Christmas cactus. If these plants are exposed to more than 12 hours of light per day, blooming of flowers do not take place. The plants mentioned here thus belong to short day plants.