RQ value in succulent xerophytes (Bryophyllum) is

Options

A. One
B. More than one
C. Less than One
D. Zero

Answer

### Step-by-Step Solution:

1. **Understanding RQ (Respiratory Quotient)**:
- RQ is defined as the ratio of carbon dioxide (CO2) produced to oxygen (O2) consumed during respiration.
- The formula for RQ is:
\[ RQ = \frac{CO2 \text{ produced}}{O2 \text{ consumed}} \]

2. **Identifying the Nature of Substrate**:
- The RQ value varies depending on the type of substrate being metabolized:
- Carbohydrates: RQ = 1
- Proteins: RQ = 0.8 to 0.9
- Fats: RQ = 0.7

3. **Specific Case of Bryophyllum**:
- Bryophyllum is a succulent xerophyte that has adapted to arid conditions.
- In Bryophyllum, carbohydrates are partially oxidized to produce malic acid.

4. **Analyzing the Reaction**:
- The reaction can be simplified as:
\[ 2 \text{ molecules of glucose} + 3 \text{ molecules of oxygen} \rightarrow 3 \text{ molecules of malic acid} + 3 \text{ water} + \text{ energy} \]
- In this reaction, CO2 is not released, but oxygen is consumed.

5. **Calculating RQ for Bryophyllum**:
- Since no CO2 is produced, the numerator in the RQ formula is 0.
- Therefore, the RQ value can be calculated as:
\[ RQ = \frac{0 \text{ (CO2 produced)}}{3 \text{ (O2 consumed)}} = 0 \]

6. **Conclusion**:
- The RQ value for Bryophyllum is 0.

### Final Answer:
The RQ value in succulent xerophytes (Bryophyllum) is **0**.