9.2 - Transport in Angiospermophytes

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9.2 - Transport in Angiospermophytes
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Transport in Angiospermophytes
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Minerals in the Soil

• Minerals must be able to move through the soil to
  the roots of plants to be absorbed - how do they
  do this?
• Diffusion -
• Fungal hyphae -
• Dissolved in soil water -

9.2.2
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Mineral Uptake

• Minerals are absorbed by the plant via active
  transport
• Minerals include potassium, phosphate, nitrates
  and other ions
• The concentration of ions is higher inside the
  root cell than in the surrounding soil
• Move against the concentration gradient
• Allows for selective absorption of minerals by
  plants
• Cortex cells absorb mineral ions that are
  dissolved in water
• From cortex, minerals dissolved in water travel
  through the endodermis and into the vascular
  cylinder.

9.2.3
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Mineral Uptake
9.2.3
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Mineral Uptake
9.2.3
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Vascular Tissue - Xylem

• Xylem water and mineral conducting tissue
• At maturity, cells are dead and lack plasma
  membranes so water flows through freely
• End walls break down forming long tubes
• Pores in side walls allow water movement between
  adjacent cells

9.2.6
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Vascular Tissue - Xylem

• Composed of tracheids and/or vessel elements
• Tracheids
• Narrow cells arranged in columns
• Overlapping ends help with support and water
  movement
• Vessel Elements
• Cell wall arranged in a helical pattern that
  enable walls to withstand pressure and stretch as
  other living cells grow
• Wide diameter allows for efficient water
  transport
• Only found in angiosperms

9.2.6
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Vascular Tissue - Xylem
9.2.6
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Vascular Tissue - Xylem
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Transpiration

• Transpiration - the loss of water vapor from the
  leaves and stems through evaporation
• Plants are adapted to limit water loss how?

9.2.5 9.2.6
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Transpiration
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Transpiration Stream

• Transpiration stream - transpiration creates a
  flow of water from the roots, through the stems,
  to the leaves
• Movement of water through plants depends on the
  cohesion and adhesion of water molecules - what
  are these properties?
• Water forms a column due to hydrogen bonding

9.2.6
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Transpiration Stream

• Steps in water movement
• Water evaporates from spongy mesophyll in leaf
  tissue (transpiration)
• Water is replaced with water from xylem tissue in
  leaf veins
• Water moves into leaf tissue via capillary action
• When water is pulled out of xylem, suction
  develops, and more water is pulled up from roots
  and stem transpiration pull
• Like using a straw to suck up liquid

9.2.6
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Transpiration Stream
9.2.6
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Regulation of Transpiration

• Water evaporates out of the leaf tissue through
  the stomata (transpiration)
• Guard cells control transpiration by opening and
  closing the stomata
• Generally, guard cells open stomata during the
  day and close them at night - why?

9.2.7
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Regulation of Transpiration

• Changes in turgor pressure in the guard cells
  open and close the stomata
• Guard cells actively uptake potassium ions (K)
  and increase solute concentration
• Water enters the guard cells by osmosis to
  balance solute concentration and cells become
  turgid.
• Turgid guard cell open stomata
• Reverse process makes guard cells flaccid and
  closes stomata
• Flaccid guard cell closed stomata

9.2.7
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Regulation of Transpiration
9.2.7
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Regulation of Transpiration
9.2.7
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Regulation of Transpiration

• Environmental factors and stressors can also
  affect transpiration and opening and closing of
  the stomata
• When plants are water deficient, cells may lose
  turgor and stomata close - why important?
• Abscisic acid, a plant hormone, signals stomata
  to close during water deficiencies.

9.2.8
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Factors Affecting Transpiration

• Factors affecting transpiration
• Light guard cells close in darkness, open in
  light why?
• Increased transpiration during day
• Temperature higher temperatures increase
  transpiration
• Also decrease outside humidity thus increase
  diffusion out water out of leaf

9.2.9
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Factors Affecting Transpiration

• Factors affecting transpiration
• Humidity lower humidity increases transpiration
  why?
• Wind air movement moves air saturated with
  water vapor away from stomata thereby
  increasing transpiration

9.2.9
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Xerophytes

• Plants adapted to grow in very dry environments
• Have evolved different adaptations to help reduce
  transpiration - why?

9.2.10
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Xerophytes

• Adaptations of Xerophytes
• Spines instead of leaves why?
• Thick stems with water storage tissue
• Thick, waxy cuticle
• Vertical stems instead of lateral reaching
  branches why?
• Wide-spreading network of shallow roots why?

9.2.10
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Vascular Tissue - Phloem

• Phloem sugar and amino acid conducting tissue
• Formed from long chains of sieve-tube members
• Alive a maturity (however they lack nuclei and
  ribosomes)
• End walls (sieve plates) have pores that allow
  for flow of sugar between cells
• Each sieve tube cell has an adjacent companion
  cell that helps serve sieve tube member

9.2.11
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Vascular Tissue - Phloem
9.2.11
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Translocation

• Translocation movement of substances from one
  area in a plant to another
• Moves sugars and amino acids from source areas
  (photosynthetic tissue and storage organs) to
  sinks (fruits, seeds, and roots)
• Active process that occurs in phloem

9.2.11
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Translocation

• How Translocation Works
• Plasma membranes in sieve tube members pump
  organic compounds into cell via active transport
• Creates high solute concentration inside sieve
  tube member
• Therefore, water diffuses into sieve tube via
  osmosis - forms sap (sugars dissolved in water)
• Creates pressure inside sieve tube and pushes sap
  throughout plant

9.2.11
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Translocation
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Translocation

1. Sugar loading in sieve tube raises solute
   concentration and draws in water
2. Water influx increases pressure forcing flow of
   sap
3. Sugar unloading lowers solute concentration,
   water effluxes and pressure decreases
4. Water pulled back up via transpiration stream

9.2.11
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Translocation
9.2.11