Bryophyta are not tall plants due to:-

Options

A. Absence of meristern
B. Absence of vascular tissues
C. Presence of root system
D. All the above

Answer

### Step-by-Step Solution:

1. **Understanding Bryophyta**:
- Bryophyta, commonly known as mosses, are non-vascular plants. They are typically small and grow close to the ground.

2. **Identifying Key Features**:
- Bryophyta lack a vascular system, which includes xylem and phloem. These tissues are essential for the transport of water, nutrients, and food throughout the plant.

3. **Role of Vascular Tissues**:
- Vascular tissues (xylem and phloem) are crucial for the stability and height of plants. Xylem is responsible for transporting water and minerals from the roots to the rest of the plant, while phloem transports food produced during photosynthesis.

4. **Consequences of Absence of Vascular Tissues**:
- Without xylem and phloem, Bryophyta cannot efficiently transport water and nutrients. This limitation restricts their growth potential, preventing them from becoming tall plants.
- Additionally, the lack of a vascular system means that Bryophyta are generally soft and not very stable, which further inhibits their ability to grow tall.

5. **Evaluating the Options**:
- Option A: Absence of male stem - This is not a reason for their height limitation.
- Option B: Absence of vascular tissues - This is the correct answer as it directly relates to their inability to grow tall.
- Option C: Presence of root system - Bryophyta do have structures that resemble roots, but they do not function like true roots in vascular plants.
- Option D: All of the above - This is incorrect as only option B is valid.

6. **Conclusion**:
- The correct answer is **Option B: Absence of vascular tissues**. This absence is the primary reason why Bryophyta are not tall plants.