Hormone that inhibits the plant metabolism and seed germination.

Answer

**Step-by-Step Solution:**

1. **Identify the Hormone**: The hormone that inhibits plant metabolism and seed germination is known as abscisic acid (ABA).

2. **Function of Abscisic Acid**: Abscisic acid plays a crucial role in regulating various physiological processes in plants. It is primarily known for its role in promoting dormancy in seeds and inhibiting germination.

3. **Mechanism of Action**: Abscisic acid inhibits metabolism by affecting the biochemical pathways within the plant. It helps in maintaining seed dormancy, which prevents seeds from germinating under unfavorable conditions.

4. **Role in Stomatal Closure**: ABA is also involved in the closure of stomata, which are small openings on the surfaces of leaves. This closure helps the plant conserve water during stressful conditions, such as drought.

5. **Stress Response**: By promoting stomatal closure and maintaining seed dormancy, abscisic acid helps plants withstand stressful environmental conditions. When favorable conditions return, the seeds can germinate.

6. **Conclusion**: In summary, abscisic acid is the hormone that inhibits plant metabolism and seed germination, playing a vital role in plant survival during adverse conditions.

---