Classial experiment to prove essentially of `CO_(2)` for photosynthesis was given by

Options

A. Arnon
B. Von Moll
C. Calvin et al
D. Hill

Explanation

To solve the question regarding the classical experiment that proved the essentiality of CO₂ for photosynthesis, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Scientist**: The experiment that demonstrated the necessity of carbon dioxide (CO₂) for photosynthesis was conducted by the scientist named Jan Ingenhousz. However, the specific experiment referred to in the question is known as "Moll's Half-Leaf Experiment," attributed to the scientist Thomas von Moll.

2. **Understand the Experiment**: Moll's Half-Leaf Experiment involved taking a leaf from a plant and dividing it into two halves. One half of the leaf was exposed to air, while the other half was enclosed in a test tube containing potassium hydroxide (KOH).

3. **Role of Potassium Hydroxide**: Potassium hydroxide has the property of absorbing carbon dioxide from the air. Therefore, the half of the leaf that was enclosed in the KOH solution was deprived of CO₂.

4. **Conducting the Experiment**: After a certain period, both halves of the leaf were tested for the presence of starch, which is an indicator of photosynthesis. The half of the leaf that was exposed to air (and thus had access to CO₂) showed a positive starch test (indicating photosynthesis occurred), while the half enclosed in KOH showed no starch (indicating no photosynthesis).

5. **Conclusion**: The results of the experiment demonstrated that the half of the leaf that had access to CO₂ produced starch, while the half that was deprived of CO₂ did not. This clearly indicated that CO₂ is essential for the process of photosynthesis.

6. **Final Answer**: The correct answer to the question is that the classical experiment to prove the essentiality of CO₂ for photosynthesis was given by Thomas von Moll.