A decrease in photosynthetic rate with increased availability of oxygen is called

Options

A. Warburg effect
B. Richmond Lang effect
C. Blackman's Law of limiting factors
D. Emerson's enhancement effect.

Answer

To answer the question about the decrease in photosynthetic rate with increased availability of oxygen, we will analyze the options given and identify the correct term associated with this phenomenon.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a term that describes the decrease in the rate of photosynthesis when oxygen levels increase.

2. **Reviewing the Options**:
- **Option 1: Warburg Effect**: This effect is known to describe the phenomenon where an increase in oxygen concentration leads to a decrease in photosynthesis, particularly in C3 plants due to photorespiration.
- **Option 2: Richmond-Lang Effect**: This effect refers to the delay of leaf senescence caused by cytokinins and does not relate to photosynthesis or oxygen levels.
- **Option 3: Blackman's Law of Limiting Factors**: This law states that the rate of a process is limited by the factor that is in the shortest supply, but it does not specifically address the relationship between oxygen and photosynthesis.
- **Option 4: Emerson's Enhancement Effect**: This effect refers to the increased rate of photosynthesis when chloroplasts are exposed to specific wavelengths of light and does not relate to oxygen levels.

3. **Identifying the Correct Answer**: Based on the definitions and explanations of the options:
- The **Warburg Effect** is the correct answer because it specifically describes the decrease in photosynthetic rate with increased oxygen availability due to competition between oxygen and carbon dioxide during the process of photorespiration in C3 plants.

4. **Final Answer**: The correct term for the decrease in photosynthetic rate with increased availability of oxygen is the **Warburg Effect**.