Why don't winter field-grown vegetables freeze? A thorough explanation of the surprising mechanisms

Hello. I am Takahiro Ogawa, an agricultural management supporter. As the winter cold becomes more severe, many people may worry that field-grown vegetables might freeze. However, surprisingly, many field-grown vegetables do not wither and continue to grow vigorously even in the cold winter when frost falls.

The reason for this is that vegetables possess various mechanisms to protect themselves from the cold.

1. Increasing the concentration of internal substances
When it gets cold, vegetables increase the concentration of sugars, amino acids, and other substances within their bodies. These substances act like antifreeze, preventing water from freezing and inhibiting the cells from freezing.

In particular, sugar also contributes to the sweetness of vegetables. The reason winter vegetables are sweet and delicious is that they store sugar as a countermeasure against the cold.

2. Strengthening cell walls
Vegetables increase their resistance to cold by strengthening their cell walls. The cell wall is a sturdy membrane on the outside of plant cells that plays a role in maintaining the cell's shape and protecting it from external stimuli.
When it gets cold, vegetables increase the components that make up the cell walls and thicken them to prevent the cells from freezing.

3. Reducing water content
Vegetables prevent freezing by reducing the amount of water in their bodies. Since water expands when it freezes, it can cause cell destruction.
When it gets cold, vegetables reduce their internal water content by closing their stomata and suppressing water absorption from the roots.

4. Entering dormancy
Some vegetables enter a dormant state when winter arrives. Dormancy is a state in which a plant temporarily stops growing and reduces energy consumption.
While the above-ground parts of dormant vegetables may wither, they survive as underground parts or seeds and begin to grow again when spring arrives.

5. Producing freeze-tolerant proteins
Some vegetables produce special proteins called freeze-tolerant proteins. These proteins have the effect of inhibiting the growth of ice crystals within cells and preventing cell destruction.

6. Converting sugar into starch
Vegetables produce sugar through photosynthesis during the day, but when they cannot photosynthesize at night or due to cold, they convert sugar into starch and store it. Starch is harder to freeze than sugar, making it an effective countermeasure against the cold.

7. Selective breeding
Currently, varieties of vegetables that are resistant to cold have been developed. These varieties work the above mechanisms more efficiently or possess genes that increase their resistance to cold.

The reason winter field-grown vegetables do not freeze is that these various mechanisms work in combination. Vegetables possess surprising abilities to survive without succumbing to the cold.

Because winter vegetables store sugar as a countermeasure against the cold, they are generally said to be sweet and delicious. Please try tasting seasonal winter field-grown vegetables.

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