Where is sporopollenin present in plants? State its significance with reference to its chemical nature.

Explanation

**Step-by-Step Solution:**

1. **Definition of Sporopollenin:**
- Sporopollenin is a robust organic substance found in the pollen grains of flowering plants. It is known for its durability and resistance to various environmental conditions.

2. **Location of Sporopollenin:**
- Sporopollenin is specifically located in the exine layer of the pollen grain. The pollen grain consists of two main layers: the exine (outer layer) and the intine (inner layer). Sporopollenin is a key component of the exine.

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