How Do Freezing Temperatures Affect Plants?
Introduction | Puzzle | Article | Experiments

"What's Missing?" Puzzle
Which words are missing from this article? Use the word bank to fill in the blanks.

Defense Against Freezing
Not all plants react to freezing temperatures the same way. Native plants that originated in ______ climates have adaptations to survive typical winter conditions. Plants that originated in more ________ locations have fewer _________ against freezing temperatures.

What Happens Inside
Most plants contain more than 85% water. As water freezes, it ________. When this happens, cell walls and other parts of the plant can rupture. Frozen water between cells can also draw water out of the cells, causing them to ________ and _______. Hard ice crystals that form between or within the cells cause the most ___________. The _________ can be like miniature needles, piercing cell walls inside in the plant.

Water and Plants
There are many _______ of cells inside the ______ and stem of a plant. Winter-hardy plants have some _________ against freezing. Water inside the cells isn't pure water. The water in the living parts of cells contains dissolved salts, sugars, and other substances that act like anti-freeze. These substances lower the temperature at which the water freezes. This "anti-freeze water" can still ______ if temperatures drop suddenly or extremely.

Plant Adaptations
If a plant is to survive freezing __________, it needs to protect cells from ice crystals, or prevent crystals from growing too big. Here are some cool plant adaptations:

  • Seeds: Plants that only have an annual cycle get through the winter by making dry seeds which can __________ freezing.
  • Toughening/"Anti-freeze": Some plants toughen up or become _______ in the fall in response to slowly decreasing temperatures. Most produce _______ and ______ that prevent ice crystals from forming or growing large. They also gradually lose water; the drier tissues are less likely to freeze.
  • Leaf Loss: Some plants simply lose their leaves altogether and store energy in their _______. Others, such as spruce trees, have needle-like leaves with waxy coatings; these prevent water loss and cold damage.
  • Controlling Water Location: Some plants keep ______ in cell walls, but move it out of the living part of the cell where ice could kill the plant.
  • Underground Storage: Some plants, like tulip bulbs, store energy in underground structures. At planting depth, temperatures ________ fall much below 30 degrees Fahrenheit. The sugars in a hardy bulb, just like salt on a winter sidewalk, lower the temperature at which water freezes.

Frozen Tulips?
If you have a spring snow or freeze, what will happen to your tulips? The plants should be fine at 20 or 25 °F. Below those temperatures, any ______ part of the plant will be damaged and not able to make food for next year's bulb. If a tender flower bud freezes, it probably won't _________.

Dangerous Thaw
The process of thawing out can be more dangerous than freezing! Water can flow back to a damaged cell and cause it to ______. You can see evidence of this process when you look at leaves after taking them out of the freezer and watch what happens as they thaw.

Dangerous Conditions
Even a hardy plant can suffer or die under certain winter conditions. These include the following:

  • When temperatures fall below a plant's maximum low-temperature limit even after it has acclimated or toughened up
  • When early freezes occur before the plant has ___________ in the fall
  • When unusually late freezes occur in the spring after the plant has emerged
tulip in snow
Tulips in the snow


Word Bank

acclimated
bloom
burst
cold
crystals
damage
defenses
expands
freeze
frozen
hardy
layers
leaf
protection
rarely
roots
rupture
salts
shrink
sugars
survive
temperatures
tropical
water

leaf cross-section
Layers of leaf cells
leaf diagram
Diagram of leaf cells
Ice Crystal
Credit: Greg Rob
Ice crystal

 

 

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