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Stomata, Transpiration & Abscission

Stomata, Transpiration & Abscission. Stomatal Opening. Controlled by guard cells Flaccid Little water Limp Turgid Fill with water Bend http://academic.kellogg.edu/herbrandsonc/bio111/animations/0021.swf. Opening of Stomata. Triggered by blue light

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Stomata, Transpiration & Abscission

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  1. Stomata, Transpiration & Abscission

  2. Stomatal Opening • Controlled by guard cells • Flaccid • Little water • Limp • Turgid • Fill with water • Bend • http://academic.kellogg.edu/herbrandsonc/bio111/animations/0021.swf

  3. Opening of Stomata • Triggered by blue light • Yellow pigments located in membrane (?) • Activates proton pump • H+ out, creates electrochemical gradient • K+ diffuses in through ion channels, Cl- follows • K+, Cl- accumulate in vacuoles, water moves in

  4. Closing of Stomata • K+ concentration in guard cells decrease during day • Sucrose increases, maintains osmotic pressure • As sucrose concentration decreases, water leaves • Pores close

  5. Factors Affecting Stomatal Opening & Closing • Blue Light • Low CO2 concentration • Water stress • Hormones • Abscisic acid

  6. Water Loss • Transpiration • 99% of water plants take in is lost by evaporation • Open stomata • Rate of Transpiration affected by: • Humidity • Temperature • Wind • Guttation • Liquid water forced out when transpiration negligible

  7. Transpiration

  8. Importance of Transpiration • Allows water to move from roots to leaves

  9. Abscission • Shedding of leaves

  10. Abscission • Conifers lose needles year-round • Deciduous trees • Survive low temp of winter • Water uptake inhibited • Prevents continuous water loss by transpiration • Controlled by hormones: Ethylene

  11. Essential organic compounds & minerals move to other parts of plant for storage • Chlorophyll breaks down, other pigments seen • Cork forms protective layer on stem side of abscission zone of petiole • Enzymes dissolve middle lamella in abscission zone of petiole • Leaf detaches in breeze

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