Lecture 5 and 6

Lecture 5 and 6 - Lecture 5 LECTURE NOTES FOR PLANT...

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Lecture 5 – LECTURE NOTES FOR PLANT SOLUTIONS TO COLD AND SNOW AND HEAT; ANIMAL SOLUTIONS TO HEAT PLANTS IN WINTER DEEP SNOW PROBLEM : PHYSICAL DAMAGE DUE TO WEIGHT OF THE SNOW SOLUTIONS : 1) LOSS OF LEAVES 2) SMALL LEAVES (CONIFER NEEDLES OR BOG PLANTS SUCH AS LEATHERLEAF, LABRADOR TEA 3) TREES CAN HAVE A SHAPE THAT SHEDS SNOW: SPIRE SHAPE (BALSAM FIR) OR SPINDLY SHAPE (SPRUCE) – for shedding snow PLANT LEAVES POSE ANOTHER PROBLEM IN WINTER = DESSICATION (DRYING OUT) SOLUTIONS: 1) HAVE THE LEAVES FALL OFF (ALL DECIDUOUS TREES AND LARCH OR TAMARACK drops its needles) – most conifers maintain their needles throughout the season 2) LEAVES STAY ON BUT HAVE ADAPTATIONS SUCH AS SMALL SURFACE AREA, WAXY CUTICLE, CLOSED STOMATA, HAIRY UNDERSIDES Plants protect themselves from frost and dehydration stress with antifreeze proteins, heat- shock proteins and sugars (sucrose is common). LEA (late embryogenesis abundant) protein expression is induced by stresses and protects other proteins from aggregation as a result of desiccation and freezing Coniferous trees – their needles don't hold snow due to small surface area – may be an adaptation as well as the shape of the tree, easily hold the snow. Includes a pointed shape or a rounded (small rounded surface on top) like spruce trees far north, or balsam firs (insect defence by producing type of hormones, a church steeple shape). Good for birds every adaptation has a drawback to it – for the trees having these shapes, a negative is their height (weakness of the tree), but more importantly, are cut down for Christmas trees. Deep snow causes branches to break (jack pines for example) PROBLEM OF HAVING WATER INSIDE PLANT TISSUES FREEZE – THERE IS NO ANTIFREEZE IN PLANTS – water turns to ice COLD HARDY = FREEZE TOLERANT PLANTS HAVE ICE BETWEEN CELLS, BUT NOT INSIDE THEM (or they would burst) THE ICE PENETRATES THE CELL WALLS BUT NOT THE CELL MEMBRANE MEMBRANE BECOMES MORE ELASTIC AND ALLOWS WATER TO LEAVE CELLS, MAKING THE SOLUTE MORE CONCENTRATED AND ALLOWING THE LIQUID TO SUPERCOOL INSIDE THE CELLS. Solution: go dormant during extreme cold temperature, so they basically shut down (many plants) surface area in animals via curling up, trees also curl up the ends of their leaves/branches to keep them protected Supercooling is the process of chilling a liquid below its freezing point, without it becoming solid – allowing water in tissues not to turn into ice (which would cause the cells to burst and ultimately the plant to die). Freeze tolerance is another method, control where the ice forms (do not allow ice to form inside body tissues which would be fatal).
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In plants, this freeze tolerance is called 'cold hearty' – process to be able to withstand ice inside tissues and plants is called cold hartedness. Inside the cell, the membrane in plants that are cold hardy, ice crystals are able to penetrate cell walls, because
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This note was uploaded on 08/13/2008 for the course BIOL 1902 taught by Professor Runtz during the Winter '08 term at Carleton CA.

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Lecture 5 and 6 - Lecture 5 LECTURE NOTES FOR PLANT...

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