Which of the following is absent in the primary and secondary structure for stem of Pinus

Options

A. (a) Sieve tubes
B. (b) Mucilage duct
C. (c) Companion cells
D. (d) Phloem parenchyma

Answer

To determine which structure is absent in the primary and secondary structure of the stem of Pinus, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Plant Type**: Recognize that Pinus is a gymnosperm, which means it is a non-flowering plant. Gymnosperms are generally considered less advanced than angiosperms, which are flowering plants.

2. **Understand the Structures**: Familiarize yourself with the different structures mentioned in the options:
- **Seed Tubes**: Present in both gymnosperms and angiosperms.
- **Mucilage Ducts**: Also present in both types of plants.
- **Companion Cells**: Specific to angiosperms; absent in gymnosperms.
- **Phloem Parenchyma**: Present in both gymnosperms and angiosperms.

3. **Analyze Each Option**:
- **Option A (Seed Tubes)**: Present in both gymnosperms and angiosperms.
- **Option B (Mucilage Ducts)**: Present in both gymnosperms and angiosperms.
- **Option C (Companion Cells)**: Absent in gymnosperms; present in angiosperms.
- **Option D (Phloem Parenchyma)**: Present in both gymnosperms and angiosperms.

4. **Identify the Absence**: Since companion cells are specifically mentioned as being absent in gymnosperms, including Pinus, this is the structure that does not exist in the primary and secondary structure of the stem of Pinus.

5. **Conclusion**: The answer to the question is **C (Companion Cells)**, which are absent in the primary and secondary structure for the stem of Pinus.

### Final Answer:
C (Companion Cells)

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