Cryopreservation is germplasm protection by

Options

A. Crossing with wild varieties.
B. Energy flow in different trophic levels
C. Both A and B
D. Low temperature.

Answer

**Step-by-Step Solution:**

1. **Understanding Cryopreservation**: Cryopreservation is a technique used to preserve biological tissues, including cells, tissues, and seeds, by cooling them to very low temperatures.

2. **Temperature Ranges**: The preservation occurs at specific low temperatures:
- **-80°C**: This temperature is typically achieved using solid carbon dioxide (dry ice).
- **-196°C**: This temperature is achieved using liquid nitrogen.

3. **Purpose of Low Temperatures**: The primary reason for using such low temperatures is to halt enzymatic and metabolic activities that could lead to damage. By stopping these activities, the integrity of the germplasm is maintained.

4. **Evaluating Options**:
- **Option A**: "Crossing with wild varieties" - This is a method of hybridization and is not related to cryopreservation.
- **Option B**: "Energy flow in different trophic levels" - This concept is unrelated to germplasm protection.
- **Option C**: "Both A and B" - Since both A and B are incorrect, this option is also incorrect.
- **Option D**: "Low temperature" - This is the correct answer as it directly relates to the process of cryopreservation.

5. **Conclusion**: Therefore, the correct answer to the question "Cryopreservation is germplasm protection by" is **D: Low temperature**.

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