Absolute Zero and the Conquest of Cold  




Topic 11: Agriculture

Agriculture has benefitted from low-temperature science in numerous ways. The most dramatic effect has come from the simple introduction of the refrigerator and freezer. Agricultural products can now be stored for an extended time without resorting to canning fruit or drying meat. Not only can people keep vegetables from the garden around longer, but also foods can easily be shipped around the world so shoppers now find strawberries -- which grow only in warm temperatures -- in the supermarket in the winter. (For a price!)

While basic refrigeration has had a profound effect on farmers' lives worldwide, far lower temperatures are now used in agriculture as well. The field of cryopreservation -- storage at temperatures of -196 C or lower -- is put to use for artificial insemination of livestock and preserving plant seeds. Breeding livestock for special traits has long been a tradition on farms, so being able to store a male animal's sperm for artificial insemination gives farmers much more flexibility.

Breeding for specific traits can eventually have repercussions too. When it comes to plants it's estimated that since 1900 about 75percent of crop diversity has been lost as growers have focused on hardier or pest-resistant plants. But what's good for growing in one area of the world now might not turn out to be good for another part of the world later on. Or if a new disease attacks a crop, one might wish to incorporate genes from a different plant to increase resistance. To preserve plants for future agriculture, some 1,470 gene banks around the world are trying to maintain more than 5.4 million samples of plants, the vast majority of which are crop plants.

Most of these samples are stored as seeds. The majority of seeds won't deform when frozen at sub-zero temperatures (see the activity on animalsfor more information on why freezing a cell can destroy it). These seeds are dried and kept in deep freezers, where they can survive for up to 200 years with minimal degradation. But a lot of seeds need more care -- they need to be flash frozen so quickly that they don't change shape. Such seeds are usually stored in liquid nitrogen at -320 F (-196 C). This temperature is so cold that everything in the seed ceases to function. Scientists think a seed could remain intact like this for hundreds or even thousands of years, ensuring the diversity of crops for centuries to come.

Additional Resources


More Topics

  • Topic 1: Measuring the Cold - Thermometers
  • Topic 2: Understanding Heat and Energy
  • Topic 3: States of Matter
  • Topic 4: Refrigeration
  • Topic 5: Cryogenics
  • Topic 6: The Quest for Absolute Zero
  • Topic 7: How Animals Survive the Cold
  • Topic 8: Superconductivity
  • Topic 9: Astronomy
  • Topic 10: Spaceflight
  • Topic 11: Agriculture
  • Topic 12: Cold Medicine
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