Plants

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Plants
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Evolution

• Non Vascular, no seeds
• Vascular, no seeds
• Vascular with seeds

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Non vascular

• Bryophytes moss
• No vascular tissue xylem and phloem
• No roots (tiny cellular threads)
• No leaves (thin layer of cells for photosynthesis)

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Vascular Plants

• All vascular plants do alternation of generations
• Fern (Lycophytes)
• no seeds
• Yes leaves
• Roots rhizome (lateral)
• With mycorrhizal fungi

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Vascular plants with seeds

• Gymnosperm

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Vascular plants

• angiosperm

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Proton Pump

• Plants use proton pumps extensively
• The pump uses energy from ATP to pump H across
  the cell membrane
• This gives the cell potential energy
• More negative inside. (voltage)
• Lower concentration of H inside
• Plants use this energy to drive transport of
  solutes.

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Water potential

• Osmosis
• Diffusion
• Water potential
• solute concentration pressure

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Compartments

• Cell wall
• Semi permeable cell membrane cytosol
• Vacuole vacuolar membrane tonoplast
• Symplast Plasmodesmata holes that connect one
  plant cell to next. Continuuum of cytoplasm.
• Apoplast continuum of cell walls

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Bulk Flow

• Long distance transport
• Bulk flow movement of fluid driven by pressure.
• In Phloem, loading of sugar generates a high
  positive pressure at one end of a sieve tube,
  forcing sap to the opposite end of the tube.
• In Xylem, it is tension (negative pressure) that
  drives transport
• Transpiration
• Cohesion
• Absorption at root

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Roots

• Root hairs
• Extensions of epidermis
• Increase surface area
• Located near the root tip
• Where most absoption occurs
• Water then goes along apoplast to symplast
• Mycorrhizae symbiosis of roots and fungi
• Increase surface area (a lot) for absorption

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Roots

• Endodermis
• Innermost cells of root.
• Last semipermieable checkpoint before water and
  nutrients into vascular tissue
• Casparian strip
• Blockage at end of apoplast. So water and
  nutrients can not get into vascular tissue by
  apoplast (ie without going thru. Semipermeable
  endodermis.)

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Movement of water

• Pulling transpiration cohesion
• Pushing Root pressure
• Roots actively pump ions in water follows
• Can push more water into leaves than is
  transpired out guttation
• Guttation the water drops seen on leaves in the
  am. Happens at night due to less transpiration

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Xerophytes

• Xerophytes plants adapted to arid climates
• Small, thick, leaves