Question

DCMU inhibits
A) PSII
B) PSI
C) Destroys chloroplast
D) Inhibits oxidative phosphorylation

Answer 1

Hint: DCMU stands for Dichlorophenyl dimethyl Urea. It is an algicide or a herbicide. It is a photosynthesis blocker. It inhibits the flow of electrons. This inhibitor does not allow plants to produce chemical energy.

Complete answer:
To solve this question, we must know the function of DCMU.

The functional unit of photosynthesis is the photosystem. In this light energy is absorbed and electrons are produced and transferred.

DCMU is an algicide or a herbicide which inhibits photosynthesis. It does not allow the flow of electrons from PSII to plastoquinone by blocking its binding site. This disrupts the production of glucose by using sunlight. As there is no electron flow NADP does not get reduced to NADPH.

PSI- PSI or photosystemI absorbs the light of longer wavelength. In this system, the electron is transferred through the electron carriers called the ferredoxin. It facilitates the cyclic flow of electrons. DCMU does not cause any effect on PSI or calvin cycle.

Chloroplast- Chloroplast is the photosynthetic centre of the cell. It does not have any effect on the chloroplast.

DCMU stimulates cyclic phosphorylation. It is the main step in which ATP is formed due to the transport of electrons. It liberates oxygen. This process takes place in mitochondria.

Hence, the correct answer is option (A)

Note: PSII or photosystem II is a light harvesting unit. It absorbs shorter wavelengths of light. This protein complex uses the energy obtained from sunlight to facilitate oxidation of water, producing oxygen and supplying electrons to the electron transport chain.