When the intensity of light falling on leaf increases beyond a point, chlorphyll is destroyed. This phenomenon occurs in the presence of

Options

A. `CO_(2)` and is called photooxidatin
B. `O_(2)` and is called photooxidation
C. `O_(2)` and is called photorespiration
D. `CO_(2)` and is called photorespiration

Answer

To solve the question regarding the phenomenon that occurs when the intensity of light falling on a leaf increases beyond a point, leading to the destruction of chlorophyll, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Chlorophyll's Role**:
- Chlorophyll is a pigment essential for photosynthesis, allowing plants to absorb light energy.

2. **Identifying the Effect of High Light Intensity**:
- When the intensity of light exceeds a certain threshold, it can lead to damage in the chlorophyll molecules.

3. **Defining the Phenomenon**:
- This damage to chlorophyll due to excessive light intensity is known as **photo-oxidation**.

4. **Conditions for Photo-Oxidation**:
- Photo-oxidation occurs in the presence of oxygen (O2). This process involves the oxidation of chlorophyll when it absorbs too much light energy.

5. **Reactive Oxygen Species (ROS)**:
- During photo-oxidation, reactive oxygen species (ROS) can form, which are harmful to the plant cells and can lead to further damage.

6. **Conclusion**:
- Therefore, the phenomenon where chlorophyll is destroyed due to high light intensity is called **photo-oxidation**, and it occurs in the presence of **oxygen**.

### Final Answer:
The phenomenon is called **photo-oxidation**, and it occurs in the presence of **oxygen (O2)**.

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