Some plants require exposure to light for a period exceeding a well-defined critical duration. These plants are known as:

Assertion $(A)$: Vernalization is acceleration of subsequent flowering by low temperature treatment.
Reason $(R)$: Site of vernalization is apical meristem.

Some varieties of wheat are known as spring wheat while others are called winter wheat. The former variety is sown and planted in spring and is harvested by the end of the same season. However,winter varieties,if planted in spring,fail to flower or produce mature grains within a span of a flowering season. Explain,why?

Describe $(1)$ Photoperiodism.

Photoperiodism is:

Define/Explain: Vernalization.