Question

If the dark period of a short day plant is interrupted by a brief exposure of light, then the plant shows

Answer 1

HERE IS UR ANSWER 
Photoperiodism is the physiological reaction of organisms to the length of day or night. It occurs in plants and animals. Photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light and dark periods.
Many flowering plants  use a photoreceptor protein, such as phytochrome or cryptochrome,to sense seasonal changes in night length, or photoperiod, which they take as signals to flower.

hope it helps u 
AJ