Some herbicides control weeds by inhibiting photosynthesis. The sequence of reactions involved in the process is: (A) Production of lipid radical and initiation of chain of lipid peroxidation (B) Extraction of hydrogen from unsaturated lipids by triplet chlorophyll and singlet oxygen (C) Oxidation of lipids and proteins (D) Loss of chlorophyll and carotenoids
Choose the correct answer from the options given below:

Correct option is C

The correct answer is (C) (B), (A), (C), (D)

Explanation:
• When photosynthesis is inhibited (e.g., by Bipyridyliums like Paraquat), the energy absorbed by chlorophyll cannot be utilized for carbon fixation.
• Step (B): The excess energy results in the formation of triplet chlorophyll and singlet oxygen, which then extract hydrogen from unsaturated lipids in the cell membrane.
• Step (A): This leads to the production of lipid radicals, initiating a chain reaction of lipid peroxidation.
• Step (C): This chain reaction results in the widespread oxidation of lipids and proteins in the membrane.
• Step (D): Finally, the disintegration of membranes leads to the loss of chlorophyll and carotenoids (bleaching/browning) and ultimate cell death.

Information Booster:
• Paraquat acts as a decoy for electrons in Photosystem I, preventing the reduction of NADP and leading to the production of destructive reactive oxygen species (ROS).

Additional Knowledge:
• The visual symptom of this process is rapid wilting and desiccation of the green tissue, usually within hours of sunlight exposure.