Theory suggesting that carbon dioxide in respiration helps in mineral absorption is called

Options

A. Carbonic acid exchange theory
B. Contact exchange theory
C. Active mineral absorption
D. Donnan dquilibrium

Answer

To answer the question regarding the theory that suggests carbon dioxide in respiration helps in mineral absorption, we can analyze the options provided and understand their relevance to the concept.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a specific theory that links carbon dioxide produced during respiration to the absorption of minerals in plants.

2. **Identifying the Theories**: The options provided are:
- Carbonic acid exchange theory
- Contact exchange theory
- Active mineral absorption theory
- Donnan equilibrium

3. **Evaluating Each Theory**:
- **Donnan Equilibrium Theory**: This theory relates to the behavior of ions across a membrane but does not specifically address the role of carbon dioxide in mineral absorption. Thus, it is not the correct answer.

- **Contact Exchange Theory**: This theory suggests that ions in the soil can exchange freely and are not tightly held. While it involves ion exchange, it does not specifically mention carbon dioxide's role in mineral absorption, making it an incorrect option.

- **Active Mineral Absorption Theory**: This theory indicates that mineral absorption is an active process that requires energy (ATP). Although it describes a mechanism of absorption, it does not focus on the role of carbon dioxide, so it is also incorrect.

- **Carbonic Acid Exchange Theory**: This theory posits that carbon dioxide produced during respiration reacts with water to form carbonic acid (H2CO3). This acid then dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-), which facilitate the absorption of minerals. This theory directly links carbon dioxide to mineral absorption.

4. **Conclusion**: Based on the evaluations, the correct answer to the question is the **Carbonic Acid Exchange Theory**.

### Final Answer:
The theory suggesting that carbon dioxide in respiration helps in mineral absorption is called **Carbonic Acid Exchange Theory**.