The pigment involved in red-far red light interconversion is

Which of the following pigments absorbs red and far-red light?

Which treatment is effective in the red-far red light response of plants?

Which of the following is/are example/s of long day plant?
$I.$ Tomato
$II.$ Maize
$III.$ Rice
$IV.$ Radish
Choose the correct option accordingly.

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

In short day plants $(SDP)$,flowering is induced by