What will be the effect on phytochrome in a plant subjected to continuous red light?

The hormonal substance which migrates from leaves to shoot apices to induce flowering is

Florigen is produced in the region of

When all parts except the leaves of a short-day plant are covered with a light-proof cover and then subjected to short-day light/dark treatment,it will produce flower buds. When a portion of this plant is grafted onto another plant of the same species which has been prevented from flowering by excessive exposure to light,this latter plant will also produce flower buds. Which is the best inference from this result?

The wavelength of light absorbed by the $P_r$ form of phytochrome is (in $nm$)

The name 'phytochrome' was given by