Moll's half leaf experiment shows

Options

A. unequal transpiration from two surfaces of leaf
B. `CO_(2)` is essential for photosynthesis
C. relation between transpiration and absorption
D. chlorophyll is essential for photosynthesis

Answer

### Step-by-Step Solution for Moll's Half Leaf Experiment

1. **Understanding the Experiment Setup**:
- Take a potted green plant that is capable of photosynthesis.
- Select a healthy leaf from the plant for the experiment.

2. **Preparation of the Leaf**:
- Cover one half of the leaf with a wide-mouth bottle that contains potassium hydroxide (KOH) soaked cotton. KOH is known to absorb carbon dioxide (CO2) from the air.

3. **Discharging the Plant**:
- Before starting the experiment, ensure that the plant has been kept in darkness for a few hours to deplete the starch reserves in the leaf. This is important for the starch test later.

4. **Exposure to Light**:
- Place the entire setup in sunlight for a day. This allows the leaf to undergo photosynthesis, but only the part exposed to CO2 will be able to perform this process.

5. **Plucking the Leaf**:
- After a day of exposure to sunlight, carefully pluck the leaf from the plant.

6. **Starch Test**:
- Perform the starch test on the leaf. This involves boiling the leaf in water to kill it, then soaking it in alcohol (usually ethanol) to remove chlorophyll, and finally rinsing it in iodine solution.

7. **Observing Results**:
- The part of the leaf that was exposed to the atmosphere (not covered by the bottle) will turn bluish-black, indicating the presence of starch, which means photosynthesis occurred there.
- The part of the leaf that was covered by the bottle (and thus deprived of CO2) will show a negative starch test (it will not turn bluish-black), indicating that photosynthesis did not occur in that area.

8. **Conclusion**:
- From the results, we conclude that CO2 is essential for photosynthesis, as the part of the leaf that was able to access CO2 produced starch, while the part that could not access CO2 did not.

### Final Answer
Moll's half-leaf experiment shows that **B) CO2 is essential for photosynthesis**.