Question

Pollen grains can be stored for several years in liquid nitrogen having a temperature of

• A. –120°C
• B. – 196°C
• C. – 80°C
• D. – 160°C

Answer 1

The Correct Option is B

The storage of pollen grains in liquid nitrogen is a crucial technique in the field of biology, particularly in plant genetics and breeding. This question asks about the specific temperature at which pollen grains can be stored for several years in liquid nitrogen. Below is a detailed explanation and reasoning for the provided options:

1. Understanding Liquid Nitrogen Storage: Liquid nitrogen is commonly used to preserve biological materials, including pollen grains, for long durations. This is due to its very low temperature, which effectively slows down biological processes, thereby preventing spoilage and degradation.

2. Temperature of Liquid Nitrogen: Liquid nitrogen boils and thus maintains a temperature at approximately -196^\circ\text{C} (77\text{K} or -321^\circ\text{F}), which is significantly cold enough to preserve biological specimens for extended periods without degradation. Hence, it's frequently used in cryopreservation.

3. Analysis of the Options:

   • -120^\circ\text{C}

     This is not the typical temperature at which liquid nitrogen is maintained. Liquid nitrogen needs to be much cooler than this to be effective for biological preservation.

   • -196^\circ\text{C}

     This is the accurate boiling point of liquid nitrogen. At this temperature, biological materials such as pollen grains can be preserved effectively for several years.

   • -80^\circ\text{C}

     This is a temperature commonly achieved with dry ice, not liquid nitrogen. While it can slow metabolic processes, it is not low enough for long-term pollen preservation.

   • -160^\circ\text{C}

     This temperature is also lower than typical freezers can achieve but still not as effective as the boiling point of liquid nitrogen for optimal preservation.

4. Conclusion: Based on the properties of liquid nitrogen and its application in biological preservation, the correct answer is -196^\circ\text{C}. This is the temperature at which liquid nitrogen is maintained, making it capable of preserving pollen grains for several years.