The concentration of the essential element below which plant growth is retarded is termed as

Options

A. Limiting concentration
B. Deficient concentration
C. Critical concentration
D. Toxic concentration

Answer

To answer the question, "The concentration of the essential element below which plant growth is retarded is termed as," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Importance of Essential Elements**:
- Plants require various essential elements for their growth and development. Each element has a specific concentration that is necessary for optimal functioning.

2. **Identify the Required Concentration**:
- Each essential element has a required concentration, often expressed in terms like millimoles per kilogram (mmol/kg). This concentration is crucial for the plant's normal physiological functions.

3. **Recognize the Impact of Insufficient Concentration**:
- If the concentration of an essential element provided to the plant falls below the required level, it can lead to disruptions in the plant's normal functions. This can result in stunted growth or other physiological issues.

4. **Define the Term**:
- The specific term used to describe the concentration below which plant growth is retarded is known as "critical concentration." This term indicates the threshold level of an essential element necessary for proper plant growth.

5. **Select the Correct Answer**:
- Based on the understanding that the concentration below which growth is retarded is termed as critical concentration, we conclude that the correct answer to the question is "critical concentration."

### Final Answer:
The concentration of the essential element below which plant growth is retarded is termed as **critical concentration**.

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