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Lecture 9

BIOL 1902 Lecture Notes - Lecture 9: Abies Balsamea, Antifreeze Protein, Acer Rubrum


Department
Biology
Course Code
BIOL 1902
Professor
Michael Runtz
Lecture
9

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BIOL 1902 – Week 9
Plants during sub-zero temperatures:
- Some go dormant in soil under snow
Plants become cold hardy:
- Excess water withdrawn & evaporates from leaves & twigs
- Water drawn out of cells, which increases solute concentration
- Protective sugars added to cells increasing solute concentration
- Cell membranes become more flexible (unsaturated fatty acids added)
- Antifreeze proteins to suppress ice formation & proteins to resist dehydration
Plants become cold hardy through acclimation:
- 1st stage of acclimation triggered by change in photoperiod (daylight to darkness ratio)
oPhytochromes = light-sensitive photopigments
Cause cells to go dormant
Make plant more responsive to low temperatures
- 2nd stage triggered by cold (not sub-zero (10° - 0°C)) temperatures
- Some trees are cold hardy to -80°C
Retaining needles creates new problem:
- Damage by solar radiation
- Solution: xanthophyll pigments
oEnable chlorophyll to use sun’s energy to create heat, not photosynthesize
- Skunk Cabbage has unusual adaptation for the cold:
oTurns up the heat
oSome insects inside of it taking advantage of the heat
Desiccation (extreme dryness) = another problem:
- Conifers retain their leaves so size & shape = very important
oLeaf surface area = small – close stomata, thick cuticles, hairs on underside of
leaves
- Rock Polypody = evergreen (green all year round) fern
oReduces leaf surface area by rolling them up
- What about deciduous trees?
oSolution: lose their leaves
Red Maple Tree:
- Some have red leaves, some have yellow
oMales turn red, females turn yellow
- Red isn’t present (leaves produce anthocyanins)
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