Plant transport

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Plant transport

• Chapter 36

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Plant transport

• Evolutionary changes
• Roots, Leaves, Stems
• Water
• Carbohydrates
• Minerals
• Light energy
• CO2
• O2

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Water transport

• Roots
• Xylem
• Stomata
• Transpiration
• Cohesion adhesion

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Water transport

• Flaccid
• Limp
• Water loss
• Plasmolysis
• Cell membrane pulls away from cell wall
• Due to water loss

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Water transport

• Turgid
• Firm
• Water gain
• Healthier plant

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Water transport

• Cell to cell (short distance)
• Diffusion
• Apolplast
• Continuum formed by cell walls
• Symplast
• Continuum formed by cytoplasm of cells
• Plasmodesmata
• Connection between cytoplasm

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Cell wall
Apoplastic route
Cytosol
Symplastic route
Transmembrane route
Key
Plasmodesma
Apoplast
Plasma membrane
Symplast
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Water transport

• Root hairs absorb water minerals
• Diffuse into apoplast or symplast
• Pass through cortex
• Endodermis (inner lining of cortex)
• Casparian strip (waxy substance)
• Controls flow water/ions to xylem
• Forces flow to pass cell membrane

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Casparian strip
Plasmamembrane
Apoplasticroute
Vessels(xylem)
Symplasticroute
Roothair
Epidermis
Stele(vascularcylinder)
Endodermis
Cortex
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Xylem

• Movement based on bulk transport
• Transpiration
• Negative pressure
• Root pressure
• Positive pressure
• Upward push of water/ions in xylem
• Solar powered

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Xylem

• Guttation
• Loss of liquid through leaves
• Ends of leaves
• Increased root pressure

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Stomata

• H2O loss
• CO2 intake

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Guard cells

• Opening closing of the stomata
• Dependent on turgor pressure of guard cells
• Thicker inner cell layer
• Causes bowing of the cell when turgid
• Opens the stomata

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Guard cells

• Active K pump
• Increased K in the guard cells
• Increase in H2O in the guard cells
• Turgid
• Stomata opens
• Decreased K leads to decreased H2O
• Flaccid, stomata closes

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Translocation of Phloem Sap in Spring
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Translocation of Phloem Sap in Summer
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Carbohydrate movement

• Phloem (sieve-tube)
• Moves from source to nearest sink
• Carbohydrates enter sieve-tube cells
• Active transport
• Companion cells parenchyma cells provide the
  ATP

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Phloem
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Carbohydrate movement

• Water potential differences-created
• Water moves into the sieve-tube cells (osmosis)
• Increased turgor
• Moves carbohydrates to sink

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Carbohydrate movement

• Carbohydrates removed
• Active transport
• Water moves out (osmosis)
• Water diffuses back to xylem
• Or lost in transpiration

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