If a tree flowers thrice in a year $(October, January, \text{and } July)$ in Northern India, it is said to be

Define/Explain: Vernalization.

For short day plants,the critical period is

Vernalization is done at

Given below are two statements.
Statement $I$: If the long dark period is interrupted by a brief flash of light,short day plants will not flower.
Statement $II$: When the long dark period is interrupted by a brief flash of light,long day plants can flower.
In the light of above statements,choose the most appropriate answer from the options given below:

Phytochrome is used in