Phytochrome plays an important role in

$A$ hypothetical 'florigen' could be produced prematurely in a long-day plant by exposing it to:

Stimulus of vernalisation is perceived by

$A$: Phytochrome,a protein,has a regulatory function.
$R$: Various morphogenetic processes are regulated by it.

It is known that some varieties of wheat are sown in autumn but are harvested around next mid-summer.
$(A)$ What could be the probable reason for this?
$(B)$ What term is used for this promotion of flowering under low temperature?
$(C)$ Which plant hormone can replace the cold treatment?

What is the response of various organisms to the duration of light and dark periods called?