Chapter 37 study guide

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Chapter 37 study guide

• Six ways plant strategies regarding water.
• 1. Closing stomata account for only 1 percent
  of a leaf's surface but 90 percent of the water
  transpired. plant physiology Stomatal opening

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How it works

• Open -
• HATPase activates under blue light , pumping H
  out.
• K enters cell in response
• HCl symporter activates, carrying both into cell
• Accumulation inside cell reduces osmotic
  potential and water potential, allowing water to
  flow in swelling guard cells

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• Closed
• A signal (such as ABA, Abscisic acid, leads to
  increased intracellular Ca2
• Ca2 signals the opening of an outward channel,
  which causes membrane depolarization
• Upon depolarization K flows out, increasing
  osmotic potential and water exits.

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Water strategies

• 2. Shedding Leaves
• Deciduous plants shed their leaves annually,
  related to amount of sunlight and temperature.

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Water strategies

• 3. Develop thick leaves with few stomata
• 4 Covering surface with trichomes
• Tricomes MC - Trichomes function as devices
  against animals, as glands, as weapons or water
  vesicles, too.

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• 5. Recessing stomata in crypts or pits reduce
  desiccation because the guard cells and stomata
  (pores) are located in a deep pit

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• 6. speeding dry periods as dormant seeds
• in nature usually exists to delay germination
  until favorable environmental

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• 1. What activity causes water to be pulled up a
  stem Transpiration

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• 2. in regards to water potential which way will
  water move. Area of high water potential to one
  of lower water potential
• BIOL 230 Lecture Guide - Osmosis Animation

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Review

• Hypertonic -more solute (and hence lower water
  potential)
• Hypotonic solutions less solute (higher water
  potential).
• Isotonic equal (iso-) concentrations of
  substances. Water potentials are thus equal,
  although there will still be equal amounts of
  water movement in and out of the cell, the net
  flow is zero

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• 3. two components of water potential
• Gravity and solute concentration in each solution

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• 4 why are root hairs almost always turgid?
• Active transport by proton pumps maintains a high
  solute concentration in the root hairs.

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• 5. in the absence of transpiration, what force
  moves water up a plant?
• Water is moved up the plant by root pressure.
• Root pressure is created by the osmotic pressure
  of xylem sap which is, in turn, created by
  dissolved minerals and
• sugars

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• 6. What mechanism, other than osmosis, moves
  water through cell membranes?
• Aquaporins are water channels that transport
  water across membranes.
• BIOL 230 Lecture Guide - Transport of Substances
  Across a Membrane by Channel Proteins

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• 7. What is the effect of water potential upon
  water transport in plants?
• Water travels down the water pressure gradient
  from soil to cell or from cell to cell.

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• 8. What factors stabilize the column of water in
  xylem tissues?
• The cohesion of water molecules and the adhesion
  of water to the xylem walls results in a stable
  column of water.

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• 9. What maintains turgidity of guard cells?
• Guard cells remain turgid because of the high
  solute potential created by actively transported
  K into the cells.

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• 10. Since carbohydrates flow from a source to a
  sink without the expenditure of energy, where
  does the ATP requirement come from?
• Phloem loading and unloading requies energy

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• At their "source" - the leaves - sugars are
  pumped by active transport into the companion
  cells and sieve elements of the phloem. This
  process uses ATP as the energy source. As sugars
  and other products of photosynthesis accumulate
  in the phloem, water enters by the sieve tube
  osmosis. Sugar Transport in Plants