Helobial endosperm is restricted usually to

Options

A. Gymnosperm
B. Dicotyledons
C. Order helobiales
D. Both 2&3

Answer

### Step-by-Step Solution:

1. **Understanding Endosperm Development**:
- The endosperm is a tissue that provides nutrition to the developing embryo in seed plants. It can develop in three main ways: cellular endosperm, nuclear endosperm, and helobial endosperm.

2. **Types of Endosperm**:
- **Cellular Endosperm**: This type forms when cytokinesis occurs immediately after karyokinesis, resulting in the formation of distinct cells.
- **Nuclear Endosperm**: In this type, there is no cytokinesis; only nuclei are formed through karyokinesis, leading to a multinucleate structure.
- **Helobial Endosperm**: This is an intermediate type where both cellular and nuclear characteristics are present.

3. **Characteristics of Helobial Endosperm**:
- In helobial endosperm, the first division of the primary endosperm nucleus results in two unequal cells: a larger micropylar cell and a smaller chalazal cell.
- The micropylar cell grows faster than the chalazal cell, leading to a structure that resembles nuclear endosperm, while the chalazal cell develops more like cellular endosperm.

4. **Occurrence**:
- Helobial endosperm is typically found in the order **Helobiales**, which is a group of monocots.

5. **Example**:
- An example of a plant that exhibits helobial endosperm is **Asparagus** (Asparagus officinalis).

6. **Conclusion**:
- Therefore, helobial endosperm is restricted usually to the order **Helobiales**.

### Final Answer:
Helobial endosperm is restricted usually to the order **Helobiales**.

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