Cold hardening

Plants in temperate and polar regions adapt to winter and sub zero temperatures by relocating nutrients from leaves and shoots to storage organs.

Cold hardening is a process in which a plant undergoes physiological changes to avoid, or mitigate cellular injuries caused by sub-zero temperatures.

Plants that originated in the tropics, like tomato or maize, don't go through cold hardening and are unable to survive freezing temperatures.

Light doesn't control the onset of cold hardening directly, but shortening of daylight is associated with fall, and starts production of reactive oxygen species and excitation of photosystem 2, which influences low-temp signal transduction mechanisms.

[2] To retain the surface area of the cell membrane so it will be able to regain its former volume when temperature rises again, the plant forms more and stronger Hechtian strands.

[3] Chilling injury occurs at 0–10 degrees Celsius, as a result of membrane damage, metabolic changes, and toxic buildup.

When spring comes, or during a mild spell in winter, plants de-harden, and if the temperature is warm for long enough – their growth resumes.

Glycogen phosphorylase (GlyP) is a key enzyme that increases in comparison to a control group not experiencing cold hardening.

[8] Once warmer temperatures are observed, the process of acclimation begins, and the increase in the concentrations of glycerol and other cryoprotective compounds is reversed.

Non-diapausing insects can sustain brief temperature shocks but often have a limit to what they can handle before the body can no longer produce enough cryoprotective components.

Drosophila melanogaster (the common fruit fly) is a frequently experimented insect involving cold hardening.

In addition to the common fruit fly, the cold-hardening response of Plutella xylostella (the diamondback moth) also has been widely studied.

Once environmental temperature begins to warm up above freezing, the cold hardening process is reversed and the concentrations of glycerol and cryoprotective compounds decrease within the body.