Light is rarely a limiting factor for photosynthesis in all the following plants but is oftenly a limiting factor in

Options

A. Sciophytes
B. Heliophytes
C. Normal `C_3` plants
D. Normal `C_4` plants

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question states that light is rarely a limiting factor for photosynthesis in certain plants but is often a limiting factor in others. We need to identify which type of plants are often limited by light.

2. **Identifying Plant Types**: The question presents different types of plants:
- **Sclerophytes**: Plants that thrive in shaded areas.
- **Heliophytes**: Plants that prefer full sunlight.
- **C3 Plants**: Plants that utilize the C3 carbon fixation pathway, typically found in moderate light conditions.
- **C4 Plants**: Plants that utilize the C4 carbon fixation pathway, adapted to high light and temperature conditions.

3. **Analyzing Light Requirements**:
- **Sclerophytes**: These plants are adapted to low light conditions and can survive with minimal light. Therefore, light is rarely a limiting factor for them.
- **Heliophytes**: These plants thrive in bright sunlight and are not limited by light.
- **C3 and C4 Plants**: Both types of plants are adapted to utilize available light efficiently, and thus light is rarely a limiting factor for them.

4. **Identifying the Limiting Factor**: Since the question asks for the plant type that is often limited by light, we need to focus on the characteristics of the plants mentioned:
- **Sclerophytes** are often found in shaded areas where light is limited. Therefore, they can be affected by the lack of light more frequently than the others.

5. **Conclusion**: Based on the analysis, the answer to the question is that light is often a limiting factor in **Sclerophytes**.

**Final Answer**: Sclerophytes

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