Vernalization increases the resistance of plants for diseases caused by . . . . . . .

Nicotiana tabacum,a short-day plant,when exposed to more than the critical period of light,fails to flower. Explain.

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

Which of the following pairs is mismatched?

When flowering is regulated by the length of day and night,it is called

Explain the role of light in flowering.