1
Which pigment system is inactivated in red drop?
- PS-I and PS-II
- PS-I
- PS-II
- None of the above
Answer
(3) PS-II
Solution
Red drop (Emerson): the quantum yield of photosynthesis falls sharply when light of wavelength longer than 680 nm (far-red) is used.
As per NCERT, the reaction centre of PS I has an absorption peak at 700 nm (P700), whereas that of PS II has an absorption peak at 680 nm (P680).
⇒ Light beyond 680 nm excites only PS I; PS II is not activated, so non-cyclic electron flow (splitting of water) stops.
∴ In red drop, PS II is inactivated.
Answer: (3)
AIPMT 2001