A point at which illuminated plant parts stop absorbing `CO_(2)` from their enviroment, is known as

Options

A. (a) `CO_(2)` compensation point
B. (b) `CO_(2)` saturation point
C. (c) `CO_(2)` optimum point
D. (d) `CO_(2)` limiting point.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks about a specific point at which illuminated plant parts cease to absorb carbon dioxide (CO₂) from their environment.

2. **Identifying the Options:**
We have four options to consider:
- A) Carbon dioxide compensation point
- B) Carbon dioxide saturation point
- C) Carbon dioxide optimum point
- D) Carbon dioxide limiting point

3. **Defining the Carbon Dioxide Compensation Point:**
The carbon dioxide compensation point is defined as the concentration of CO₂ at which the rate of carbon dioxide fixation during photosynthesis equals the rate of carbon dioxide release during respiration or photorespiration. At this point, there is no net absorption of CO₂ by the plant.

4. **Explaining Why This Happens:**
At the compensation point, the amount of CO₂ that is fixed through photosynthesis is balanced by the amount of CO₂ that is released through respiration. This balance leads to a situation where the plant does not absorb additional CO₂ from its environment.

5. **Providing Specific Values:**
- For C3 plants, the compensation point typically ranges from 25 to 100 parts per million (ppm).
- For C4 plants, which are adapted to extreme conditions, the compensation point is much lower, ranging from 0 to 10 ppm.

6. **Conclusion:**
Based on the definition and explanation provided, the correct answer to the question is option A, which is the carbon dioxide compensation point.

**Final Statement:**
Hence, the correct answer is option A, carbon dioxide compensation point.

---