The essential element must be directly involved in the metabolism of the plant.

Answer

**Step-by-Step Solution:**

1. **Understanding Essential Elements**: Essential elements are nutrients that plants need to complete their life cycle. There are about 17 essential elements that plants require for their growth and development.

2. **Role of Essential Elements**: These elements are crucial for various biochemical processes in plants, including photosynthesis, respiration, and nutrient transport. They play a vital role in plant metabolism.

3. **Classification of Essential Elements**: The 17 essential elements can be classified into two categories:
- **Macronutrients**: These are required in larger quantities (e.g., nitrogen, phosphorus, potassium).
- **Micronutrients**: These are required in smaller quantities (e.g., iron, manganese, zinc).

4. **Analyzing the Statement**: The statement in question asserts that "the essential element must be directly involved in the metabolism of the plant."

5. **Conclusion**: Since essential elements are indeed involved in various metabolic processes within the plant, the statement is true.

**Final Answer**: The statement is true.

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