Transportation in Plants

1
Transportation in Plants
2
Cellular Transport Review

• Passive Transport
• - Osmosis
• - Diffusion
• - Facilitated diffusion
• Active transport
• - Ion pumps
• - Endocytosis vs. Exocytosis
• - Pinocytosis vs. Phagocytosis
• Chemiosmosis

3
Water Potential

• Water potential ? (Greek psi)
• Unit megapascal
• Mpa 10 atmospheric pressure
• Potential of pure water ? 0 Mpa
• ? ?p ?s
• If ? - number gt water move out of solution
• If ? number gt water move into the solution
• Figure 36.3
• Figure 36.4

4
Vacuole Compartment and Function

• Tonoplast vacuole membrane, regulate movements
  b/t cytosol and inside vacuole.
• Apolast continuum of cell walls_allow movements
  of water and solute across cell wall and
  extracellular spaces (fig 7.28)
• Symplast continuum b/t cells through
  plasmodermata (fig 36.6)

5
Absorption of Water and Minerals by Roots

• Root hairs/ Mycorhizea enlarge surface and
  enhance absorption of water and minerals.
• Apolastic route
• water and minerals cross cell wall --gt apoplast
  ----gt endodermis --gt ( cant pass Casparian
  strip) must pass through plasma membrane (highly
  selective regulation) --gt plasmodermata
  (symplastic) --gt Xylem vessels (fig 36.6)
• 2. Symplastic route
• water/minerals cross cell wall of epidermis --gt
  cortex cells --gt symplastic --gt xylem vessels

6
Water and Minerals Move Upwardby the T.A.C.T

• T - Transpiration creating a water potential
  difference in plant help pulling up force.
• A- Adhesion water molecules stick to xylem sap
  creates adhesion forces
• C- Cohesion water molecules stick together
  create a cohesion forces
• T-Tension tension exits in the water column due
  to cohesion of water molecules (fig 36.10)

7
Control Transpiration to Photosynthesis

• Review C3 leaf and C4 leaf (fig 35.20)
• Review C3 photosynthesis and C4 photosynthesis
• C3 pathway about 6001
• C4 pathway about 3001, (fig 10.17)
• (Trade off of C4 over head on the leave surface
  may interfere w/ function of enzymes)
• Opening and Closing of Guard Cells the process
  is not fully understood, but guard cells closing
  by uptaking K ions from the surrounding, which
  causes water diffuse into the guard cells

8
Adaptation of Xerophytes

• CAM or Crassulacean Acid Metabolism
• Small leave surface, thick leaves and thick
  cuticle
• Night time turn CO2 --gt Organic Acids
• Day time breakdown organic acids ---gt CO2 for
  photosynthesis while stomata are closing.
• (overcome overheat by storing lots of water in
  their body)

9
Transport in Phloem

• Pressure flow hypothesis active transport of
  glucose (chemiosmosis) into phloem cells cause
  water from xylem diffuse into the phloem and push
  the cytoplasm downward.
• (mesophyll sugar --gt symplastic --gt sieve tubes)
• Extra sugar is stored as starch during, but
  during winter, starch will be breakdown and move
  upward to supply food for body and leaves.
• Girdling of tree removing the bark and phloem
  kills a tree by starving the roots