A point at which illuminated plant parts stop absorbing `CO_2` from their environment , is known is

Options

A. `CO_2` compensation point
B. `CO_2` saturation point
C. `CO_2` optimum point
D. `CO_2` limiting point

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the term that describes the point at which illuminated parts of a plant stop absorbing carbon dioxide (CO2) from their environment.

2. **Identifying Key Concepts**: In photosynthesis, plants absorb CO2 to produce glucose and oxygen. However, during the night or in certain conditions, plants also respire, releasing CO2. The balance between these two processes is crucial for understanding the CO2 dynamics in plants.

3. **Defining the CO2 Compensation Point**: The CO2 compensation point is the specific concentration of CO2 in which the amount of CO2 fixed during photosynthesis equals the amount of CO2 released during respiration. At this point, there is no net gain or loss of CO2.

4. **Differentiate Between Plant Types**:
- In **C3 plants**, the CO2 compensation point typically ranges from 25 to 100 parts per million (ppm).
- In **C4 plants**, which are adapted to more extreme conditions, the compensation point is much lower, ranging from 0 to 10 ppm.

5. **Conclusion**: Based on the understanding of the CO2 compensation point and the differences between plant types, the answer to the question is that the point at which illuminated plant parts stop absorbing CO2 is known as the **CO2 Compensation Point**.

**Final Answer**: CO2 Compensation Point

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