One set of the plant was grown at 12 hours day and 12 hours night period cycles and it flowered while in the other set night phase was interrupted by flash of light and it did not produce flower. Under which one of the following categories will you place this plant?
- Long day
- Darkness neutral
- Day neutral
- Short day
Answer
(4) Short day
Solution
Short day plants are in fact long night plants: they flower only when they get a continuous dark period longer than a critical length.
⇒ With 12 h light and 12 h dark the plant flowered, so the uninterrupted night was long enough.
⇒ When the dark period was broken by a flash of light, the continuous night became shorter than the critical period and the plant did not flower.
∵ Night-break prevents flowering only in short day plants (in long day plants it promotes flowering, and day neutral plants are not affected).
∴ The plant is a short day plant.
Answer: (4)