the success of seed plants on land is mainly due to

Options

A. Presence of conducting tissue
B. Development of secondary growth
C. Evolution of siphonogamy
D. All the above.

Answer

To solve the question regarding the success of seed plants on land, we need to analyze each of the given options and determine their relevance to seed plants, also known as gymnosperms or angiosperms.

### Step-by-Step Solution:

1. **Understanding Seed Plants**:
- Seed plants, or spermatophytes, include both gymnosperms and angiosperms. They are characterized by the presence of seeds, which provide protection and nourishment to the developing embryo.

2. **Evaluating the Options**:
- **Option A: Presence of Conducting Tissue**:
- Seed plants have specialized conducting tissues, namely xylem and phloem.
- Xylem is responsible for the transport of water and minerals from the roots to the rest of the plant, while phloem transports the products of photosynthesis (food) from the leaves to other parts of the plant.
- This adaptation is crucial for the survival of plants on land, as it allows them to efficiently transport nutrients and water.

- **Option B: Development of Secondary Growth**:
- Secondary growth refers to the increase in girth of the plant, which is facilitated by the vascular cambium.
- This growth allows seed plants to become larger and stronger, enabling them to compete for sunlight and space, and to withstand environmental stresses.

- **Option C: Evolution of Siphonogamy**:
- Siphonogamy is the process involving the formation of a pollen tube, which is essential for the fertilization of ovules in seed plants.
- This adaptation allows for the transfer of sperm to the egg without the need for water, which is a significant advantage for terrestrial life.

3. **Conclusion**:
- All three options (presence of conducting tissue, development of secondary growth, and evolution of siphonogamy) contribute to the success of seed plants on land.
- Therefore, the correct answer is **D: All of the above**.