Nucleus is absent in

Options

A. Companion cells
B. Sieve tube cells
C. Phleom parenchyma
D. Cambium

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which cells lack a nucleus. We need to analyze each option provided to determine which one fits this criterion.

2. **Analyzing Companion Cells**: Companion cells are part of the phloem tissue. They are known to have a large nucleus. Therefore, companion cells cannot be the answer since they do contain a nucleus.

3. **Analyzing Sieve Tube Cells**: Sieve tube cells are also part of the phloem. When these cells mature, their nuclei break down into fragments and eventually disappear. This means that mature sieve tube cells do not have a functional nucleus. Thus, this option is a strong candidate for the answer.

4. **Analyzing Phloem Parenchyma**: Phloem parenchyma cells are living cells that do have a nucleus. Therefore, this option is incorrect as well.

5. **Analyzing Cambium**: Cambium is a type of meristematic tissue responsible for secondary growth in plants. It contains nuclei, so this option is also incorrect.

6. **Conclusion**: After analyzing all the options, the only cells that are known to lack a nucleus when mature are sieve tube cells. Therefore, the correct answer is **sieve tube cells**.

**Final Answer**: The nucleus is absent in **sieve tube cells**.

---