It is expected that `CO_(2)` concentration could reach to a level of about 600 mi`L^(-1)` by 2020 in such a case the ________ are likely to be benefitted more than the __________

Options

A. `C_(3)` plants `C_(4)` plants
B. `C_(4)` plants `C_(3)` plants
C. CAM plants `C_(4)` plants
D. `C_(4)` plants CAM plants

Answer

To answer the question regarding which plants are likely to benefit more from an increase in CO2 concentration to about 600 mL^-1 by 2020, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding CO2 Concentration**: The question states that CO2 concentration is expected to rise to 600 mL^-1. This increase in CO2 levels can influence photosynthesis in plants.

2. **Identifying Plant Types**: There are three main types of plants based on their photosynthetic pathways:
- C3 plants
- C4 plants
- CAM (Crassulacean Acid Metabolism) plants

3. **Photosynthesis in C3 Plants**: C3 plants utilize the Calvin cycle for photosynthesis, which directly uses CO2. An increase in CO2 concentration significantly enhances the rate of photosynthesis in these plants, making them more productive.

4. **Photosynthesis in C4 Plants**: C4 plants have a different mechanism that allows them to efficiently fix CO2 even at lower concentrations. They possess an enzyme called PEP carboxylase, which helps in capturing CO2. Although they can benefit from increased CO2, the extent of benefit is less compared to C3 plants.

5. **Photosynthesis in CAM Plants**: CAM plants take in CO2 at night and store it for use during the day. Their photosynthetic process is less affected by daytime CO2 levels, so they are not significantly impacted by changes in CO2 concentration.

6. **Conclusion**: Given the information, it can be concluded that C3 plants will benefit the most from the increased CO2 concentration, while C4 plants will benefit less. CAM plants will be the least affected.

### Final Answer:
It is expected that CO2 concentration could reach a level of about 600 mL^-1 by 2020; in such a case, the **C3 plants** are likely to be benefitted more than the **C4 plants**.

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