BIOL 1902 Lecture Notes - Curl

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29 Mar 2012
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LECTURE NOTES FOR WEEK SIX (ONE LECTURE ONLY)
PLANTS ALSO FACE PROBLEMS IN SUBZERO TEMPERATURES
DEEP SNOW PROBLEM:
PHYSICAL DAMAGE DUE TO WEIGHT OF THE SNOW
SOLUTIONS: 1) LOSS OF LEAVES (DECIDUOUS TREES)
2) HAVE SMALL LEAVES (CONIFER NEEDLES)
3) HAVE A SHAPE THAT SHEDS SNOW: SPIRE SHAPE (BALSAM FIR) OR SPINDLY
SHAPE (SPRUCE)
PLANT LEAVES POSE ANOTHER PROBLEM IN WINTER = DESSICATION (DRYING OUT)
SOLUTIONS;
1) HAVE THE LEAVES FALL OFF (ALL DECIDUOUS TREES AND LARCH OR TAMARACK)
2) LEAVES STAY ON BUT HAVE ADAPTATIONS SUCH AS SMALL SURFACE AREA
THEN THERE IS THE PROBLEM OF HAVING THE WATER INSIDE THE PLANT TISSUES FREEZE.
SOLUTIONS: NOTE: PLANTS DO NOT PRODUCE ANTIFREEZE
PLANTS CAN BE COLD HARDY (= FREEZE TOLERANT); PLANTS HAVE ICE BETWEEN CELLS, BUT
NOT INSIDE THEM; THE ICE PENETRATES THE CELL WALLS BUT NOT THE CELL MEMBRANE
MEMBRANES BECOME MORE ELASTIC AND ALLOWS WATER TO LEAVE CELLS, MAKING THE SOLUTE
INSIDE THE CELLS MORE CONCENTRATED. THIS ALLOWS THE LIQUID INSIDE THE CELL TO
SUPERCOOL
ACCLIMATION = THE PROCESS OF BECOMING COLD-HARDY
TWO STEPS: 1) PHOTOPERIOD: CAUSES INCREASE IN ABSCIC ACID (ABA. ABA SLOWS GROWTH,
INCREASES CELL MEMBRANE PERMEABILITY
2) FIRST HARD FROSTS = MAKES CELL MEMBRANES EVEN MORE PERMEABLE AND
INDUCES BIOCHEMICAL CHANGES INSIDE THE CELLS
SOME PLANTS AVOID REALLY SEVERE COLD TEMPERATURES BY HAVING THE PART ABOVE THE
GROUND DIE IN THE FALL AND THE PLANT SURVIVES EITHER AS SEEDS OR ROOTS IN THE
GROUND, WHICH IS COVERED BY SNOW.
SKUNK CABBAGES GENERATE THEIR OWN HEAT TO MELT SNOW IN EARLY SPRING! WHO SAID
PLANTS ARE NOT AT ALL LIKE ANIMALS!
TOO MUCH HEAT ALSO A PROBLEM FOR PLANTS AND ANIMALS:
CAN CAUSE DRYING OUT, OVERHEATING
PLANTS: SOLUTIONS:
1) REDUCE SURFACE AREA AFFECTED: CURL LEAVES
2) CLOSE STOMATA
3) ABA INDUCES PRODUCTION OF PROTECTIVE, SHOCK PROTEINS
ANIMALS: SOLUTIONS
A) SEEK COOLER SITES, SIT IN SHADE,
B) INCREASE BODY SURFACE AREA TO LOSE HEAT (FOXES STRETCH OUT, BIRDS STRETCH
WINGS)
C) BATHE, STAND IN WATER,
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