Question

Assertion: Photomodulation of flowering is a phytochrome - regulated Process.

Reason:  Active form of phytochrome (Pfr) directly induces floral induction in shoot buds.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

The correct option is: (c)

Explanation:

Flowering is a phytochrome regulated process. Phytochrome is a blue protein pigment with a molecular mass of about 125 k Da (kilodaltons). Phytochrome occurs in two interconverlible form P_r (which absorbs red light) and P_fr (which absorbs far-red light). The studies with mutants of Arabidopsis support and prove that the P_fr is the active form of phytochrome. When P_r molecules are exposed to red light, most of them absorb it and converted to P _fr. This causes floral induction in the shoot. A night interruption inhibits flowering of short-day plants and promotes flowering of long-day plants. Red light is more effective with short-day plants and a mixture of red and far-red with long-day plants.