Which of the following factor does not have direct effect on photosynthesis ?

Options

A. Temperature
B. water
C. Atmosheric `CO_(2)` concentration
D. Light

Answer

To solve the question, "Which of the following factors does not have a direct effect on photosynthesis?" we will analyze each of the provided options: temperature, water, atmospheric CO2 concentration, and light.

### Step-by-Step Solution:

1. **Understanding the Role of Temperature:**
- Temperature affects the rate of photosynthesis. Initially, as temperature increases, the rate of photosynthesis also increases due to the activation of enzymes involved in the process. However, if the temperature exceeds a certain limit, the enzymes can become denatured, leading to a decrease in the rate of photosynthesis. Therefore, temperature has a direct effect on photosynthesis.

2. **Analyzing the Role of Water:**
- Water is a crucial reactant in the light reactions of photosynthesis. However, its effect is more indirect. Water stress can cause stomata to close, reducing the availability of CO2, which in turn affects photosynthesis. Thus, while water is necessary for photosynthesis, it does not directly influence the photosynthesis process itself. Instead, it affects the plant's ability to take in CO2.

3. **Examining Atmospheric CO2 Concentration:**
- The concentration of atmospheric CO2 has a direct relationship with the rate of photosynthesis. An increase in CO2 concentration leads to an increase in the rate of photosynthesis, as CO2 is one of the key reactants in the process. Therefore, atmospheric CO2 concentration has a direct effect on photosynthesis.

4. **Considering Light Intensity:**
- Light is essential for photosynthesis, particularly for the light-dependent reactions. As light intensity increases, the rate of photosynthesis also increases, indicating a direct relationship. Thus, light has a direct effect on photosynthesis.

5. **Conclusion:**
- After analyzing all the factors, we conclude that while temperature, atmospheric CO2 concentration, and light have direct effects on photosynthesis, water does not have a direct effect. Instead, it influences photosynthesis indirectly by affecting stomatal closure and CO2 availability.

### Final Answer:
**Water** is the factor that does not have a direct effect on photosynthesis.

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