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TRANSPIRATION

TRANSPIRATION. Learning Objectives • Explain the mechanism of water uptake and movement in terms of transpiration producing a tension (‘pull’) from above, creating a water potential gradient in the xylem, drawing cohesive water molecules up the plant.

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TRANSPIRATION

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  1. TRANSPIRATION

  2. LearningObjectives • • Explain the mechanism of water uptake and movement in terms of transpiration producing a tension (‘pull’) from above, creating a water potential gradient in the xylem, drawing cohesive water molecules up the plant. • Define transpiration as evaporation of water at the surfaces of the mesophyll cells followed by loss of water vapour from plant leaves, through the stomata • • Describe how water vapour loss is related to cell surfaces, air spaces and stomata • • Describe the effects of variation of temperature, humidity and light intensity on transpiration rate • • Discuss the adaptations of the leaf, stem and root to three contrasting environments, to include pond, garden and desert, with emphasis on local examples (where appropriate) and the factors described in the core

  3. Need for transport systems • Plants need sugars and water to stay alive Water needs to travel from the roots to the leaves Sugars need to travel from the leaves to the rest of the plant Importance of water

  4. Water Movement Through a Plant

  5. Transport System in Plants Functions? Vascularbundle Xylem Phloem Sievetubes Companioncell Labeltheterms

  6. Transpiration??? How is transpirationregulated? Number of stomata Video: http://www.biologymad.com/resources/transpiration.swf

  7. http://www.phschool.com/science/biology_place/labbench/lab9/stomamov.htmlhttp://www.phschool.com/science/biology_place/labbench/lab9/stomamov.html • Tiny pores found on the surfaces of a leaf • Stomata take in carbon dioxide from the air through stomata • Water vapour passes out from the leaf to the atmosphere through stomata

  8. Whichfactorsaffectthetranspiration? Atmospheric conditions Leaf Structure

  9. LeafStructure AtmosphericStructure • Wind • Hightemperature • Lowhımidity • Highlightintensity • Thickandwaxycuticle • Stomatasunk • Humidair • Leavesshape (needle) Transpiration Rate http://twig-it.com/search#transpiration

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