Question

One set of a 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?

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

Answer 1

The Correct Option is D

The conditions show that the plant requires photoperiod shorter than the critical day length. This plant needs uninterrupted dark period for flowering. Therefore, it is a short day plant and these plants do not flower if the dark period is interrupted with flashes of light.
Long day plants require light period of $14-16$ hours for subsequent flowering. The distinctive feature of long day plant is that long night period entirely prevent flowering but long nights interrupted by light, even briefly, cause the inhibitive effect of the night to be lost and the plants flowers.
Day neutral plants flower in all photoperiods ranging from $5-24$ hrs. In these plants, floral initiation is independent of photoperiodism.