Transport in Plants

1
Transport in Plants

• DP Biology 2009

2
Root Structure Function

• Major Functions of Roots?

3
Root Structure Function

• Major Functions of Roots
• Water absorption
• Mineral absorption
• Anchoring plant into ground

4
Root Structure Function

• How does structure facilitate function?

5
Root Structure Function

• How does structure facilitate function?
• Branching
• Anchors plant to ground
• Increases SA for absorption

6
Root Structure Function

• How does structure facilitate function?
• Branching
• Anchors plant to ground
• Increases SA for absorption
• Root hairs (extensions of cell membrane)
• Increase SA for absorption

7
Root Structure Function

• How does structure facilitate function?
• Protein pumps mitochondria
• Allows for active transport of minerals

8
Root Structure Function

• How does structure facilitate function?
• Protein pumps mitochondria
• Allows for active transport of minerals
• Concentration gradient of minerals in cell
• Allows for osmosis into cell

9
Root Structure Function

• How does structure facilitate function?
• Fungal (mycorrhizal) associations
• Many plants have a
• symbiotic relationship
• with fungi in their roots
• Plant often provides sugar / nutrients
• Fungi help plants absorb minerals.

10
Mineral Uptake By Roots

• Minerals must contact membrane proteins before
  they can be absorbed.
• How does this occur?

11
Mineral Uptake By Roots

• Minerals must contact membrane proteins before
  they can be absorbed.
• How does this occur?
• SLOW diffusion

12
Mineral Uptake By Roots

• Minerals must contact membrane proteins before
  they can be absorbed.
• How does this occur?
• SLOW diffusion
• Mass flow movement / draining of ion-carrying
  water through soil

13
Mineral Uptake By Roots

• Minerals must contact membrane proteins before
  they can be absorbed.
• How does this occur?
• SLOW diffusion
• Mass flow movement / draining of ion-carrying
  water through soil
• Mycorrhizal fungi have extensive network of
  hyphae for efficient mineral absorption
• See animation http//highered.mcgraw-hill.com/si
  tes/9834092339/student_view0/chapter38/animation_-
  _mineral_uptake.html

14
Mineral Uptake By Roots

• Roots absorb minerals into root cells by
• active transport
• Ex) NO3, HPO4, K
• Minerals may be 1000X more concentrated within
  roots than within soil

15
Mineral Uptake By Roots

• Roots absorb minerals into root cells by
• active transport
• Ex) NO3, HPO4, K
• Minerals may be 1000X more concentrated within
  roots than within soil
• Minerals then passively diffuse into
• xylem for transport throughout plant

16
Water Absorption by Roots

• Water passively enters root cells via osmosis
  due to high solute concentration of minerals in
  root cells
• Most absorption through root hairs
• Water passively moves to xylem for transport
  through plant

17
Water Transport

• Water is passively transported, against gravity
  from roots to leaves, even in the tallest tree
• Only heat energy from sun is used
• HOW?

18
Water Transport

• Water is passively transported, against gravity
  from roots to leaves, even in the tallest tree
• Only heat energy from sun is used
• HOW? Tension - cohesion theory

19
Water Transport Cohesion - Tension Theory

• Water evaporating from stomata decreases water
  pressure in the leaf, creating a suction force
  known as transpirational pull.

20
Water Transport Cohesion - Tension Theory

• Water evaporating from stomata decreases water
  pressure in the leaf, creating a suction force
  known as transpirational pull.
• Water is pulled from nearest source water in
  xylem

21
Water Transport Cohesion - Tension Theory

• Water evaporating from stomata decreases water
  pressure in the leaf, creating a suction force
  known as transpirational pull.
• Water is pulled from nearest source water in
  xylem
• Water is pulled in one unbroken stream through
  xylem from roots to leaves

22
Water Transport Cohesion - Tension Theory

• Only possible due to hydrogen bonding
• Water is cohesive (sticks together)
• Water is adhesive (sticks to cellulose cell wall)

23
Water Transport Cohesion - Tension Theory

• See animation
• http//academic.kellogg.cc.mi.us/herbrandsonc/bio1
  11/animations/0031.swf

24
Xylem Structure Facilitates Water Transport

• Mature xylem consists of a long, unbroken tube of
  hollowed-out, dead cells
• Cytoplasm and end cell walls are removed from
  mature tissue
• Allows water to be pulled in unbroken stream

25
Xylem Structure Facilitates Water Transport

• Xylem side walls have pore allowing water to
  move to tissues
• Xylem wall is lignified to prevent collapse

26
Phloem Structure Function

• Phloem conducts sap (containing sucrose amino
  acids) up and down plant body
• Process called phloem translocation
• Requires energy expenditure from cell

27
Phloem Structure Function

• Unlike xylem, phloem is composed of living cells
• Cells walls have pores to allow transfer of
  nutrients

28
Phloem Structure Function

• Phloem moves from sources to sinks
• Sources
• Sinks

29
Phloem Structure Function

• Phloem moves from sources to sinks
• Sources
• Photosynthetic tissues (leaves, stems)
• Storage tissues (tap roots,
• endosperm, etc.)
• Sinks
• Roots
• Fruits / Seeds
• Growing leaves

30
Phylem Structure Function

• FYI
• Direction of phloem
• movement occurs through
• Active transport of nutrients
• Osmosis
• Pressure differences
• See animation http//highered.mcgraw-hill.com/si
  tes/9834092339/student_view0/chapter38/animation_-
  _phloem_loading.html