The phenomenon where flowering is dependent on exposure to low temperatures is known as:

Give scientific reasons:
$(1)$ Photoperiodism is essential for flowering in plants.
$(2)$ Abscission (leaf fall,flower fall,fruit fall) increases the vitality of plants.

Vernalisation is done at

All given statements are correct with respect to photoperiodism,except:

The pigment involved in red-far red light interconversion is

$A$ pigment concerned with both floral induction and seed germination is