Hort 201 Exam 2: Low Temperature Damage

Front 1

HOW CHILLING TEMPERATURES INJURE PLANTS (SLOW DEATH)

Back 1

1) Increased protein and enzyme breakdown.
2) Increased membrane leakiness

a) membranes lose selective permeability

b) often appears deeper green and slightly waterlogged

Front 2

HOW FREEZING TEMPERATURES INJURE PLANTS (SLOW OR FAST DEATH)

Back 2

1) Direct cellular damage
2) Desiccation - excessive drying-out due to cold soil and dry winds.
3) Frost heaving

4) Bark splitting

5) Physical or mechanical breakage (ice damage)

6) Sun scald or Southwest injury

Front 3

1) Direct cellular damage

Back 3

damage to individual cells.
a) Very rapid temperature drop
- ice forms in cytoplasm and ruptures cell
- seldom occurs, but always fatal

b) Moderate temperature drop
- ice forms in cell wall and cytoplasm dehydrates
- most commonly occurs, not fatal to hardy or cold acclimated plants.

Front 4

2) Desiccation

Back 4

excessive drying-out due to cold soil and dry winds

Front 5

3) Frost Heaving

Back 5

soil freezes and expands, thus heaving the plant out of the soil

Front 6

4) Bark Splitting

Back 6

canbium under bark freezes, expands, then splits the bark

Front 7

5) Physical or mechanical breakage (ice damage)

Back 7

from weight of ice on plant

Front 8

6) Sun scald or Southwest injury

Back 8

excessive desiccation on southwest side of tree; sunlight is brightest on the south and west side