The most thoroughly studied known bacteria- plant interactions is ,

Options

A. plant growth simulation by phosphate -solubilising bacteria
B. cyanobacterial syumbiosis with some aquatic ferns
C. gall formation on certain angiosperms by agrobacterium
D. nodulation of sesbania stems by nitrogen fixing bacteria

Answer

To solve the question regarding the most thoroughly studied known bacteria-plant interactions, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Bacteria-Plant Interactions**:
- Bacteria and plants interact in various ways, which can be beneficial, harmful, or neutral. These interactions can vary based on environmental conditions.

2. **Analyzing the Options**:
- **Option A**: Plant growth stimulation by phosphate solubilizing bacteria.
- **Option B**: Cyanobacterial symbiosis with some aquatic plants.
- **Option C**: Gall formation on certain angiosperms by Agrobacterium.
- **Option D**: Nodulation of Sesbania stems by nitrogen-fixing bacteria.

3. **Identifying the Most Studied Interaction**:
- Among the options, the gall formation caused by Agrobacterium is well-documented and extensively studied. This interaction involves the bacterium inducing tumor-like growths (galls) on plants, which is a significant area of research in plant pathology and genetic engineering.

4. **Conclusion**:
- The correct answer is **Option C**: Gall formation on certain angiosperms by Agrobacterium, as it is the most thoroughly studied bacteria-plant interaction.