Weedicides used in the crop fields kill the weeds by

Options

A. Preventing electron transport in respiration
B. Preventing dark phase in photosynthesis
C. Preventing light absorption by pigment
D. Preventing electron transfer in thylakoid membrane (or) in light phase

Answer

**Step-by-Step Solution:**

1. **Understanding Weedicides**: Weedicides are chemicals used in agriculture to kill unwanted plants (weeds) that compete with crops for nutrients, light, and space.

2. **Mode of Action**: The primary action of weedicides is to inhibit certain processes in the weeds that are essential for their growth and survival.

3. **Photosystem II Inhibition**: Weedicides specifically target Photosystem II (PSII), which is a crucial component of the light-dependent reactions of photosynthesis.

4. **Impact on Electron Transport**: By inhibiting PSII, weedicides block the electron transport chain that occurs during the light reactions of photosynthesis. This process is vital for the conversion of light energy into chemical energy (ATP and NADPH).

5. **Consequences of Inhibition**: When the electron transport is inhibited, the production of ATP and NADPH is reduced, which are necessary for the dark reactions (Calvin cycle) of photosynthesis. Without these energy carriers, the weeds cannot perform photosynthesis effectively, leading to their death.

6. **Correct Answer**: The correct option that describes how weedicides kill weeds is "preventing electron transport in thylakoid membrane in light phase," as this directly relates to the inhibition of the light reactions of photosynthesis.

**Final Answer**: Weedicides kill the weeds by preventing electron transport in the thylakoid membrane during the light phase of photosynthesis.

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