Plant Transport System

• 2 Transport systems

Systems

Shoot System

• Everything above ground
• Organs:
  • Leaf
  • Stem
  • etc.

Root System

• Everything below ground
• Organs:
  • Roots
  • etc.

Tissue

• Contains 3 main parts
• Dermal Tissue:
  • Outermost layer of cells
  • Provides protection and prevents water loss
• Vascular Tissue:
  • Cells involved in the transportation of substances within plants
  • Food → phloem
  • Water + Minerals → xylem
• Ground Tissue:
  • Anything else

Vascular Bundles

Root

• Phloem in a X or star shape in the middle
• Xylem surrounds it

Stem

• Xylem on the inside, Phloem on the outside
• Arranged in a circle

Leaf

• Xylem on top, phloem on the bottom

Leaf Structure

External Leaf Structure

• Lamina: Leaf blade
• Petiole: Leaf stalk
• Diocots: Net veins, veins branch off
• Monocots: Parallel veins

Functions

Lamina

• Large flat surface: Captures more sunlight
• Thin: CO2 can diffuse quickly into the inner mesophyll cells; Sunlight can reach inner cells

Petiole

• Holds lamina away from the stem to capture more sunlight
• Sessile leaves have no petiole

Veins

• Contains vascular bundles
• Xylem transports water and mineral salts to the leaf

Internal Leaf Structure

• 4 main layers:
  • Upper Epidermis
  • Palisade Mesophyll
  • Spongy Mesophyll
  • Lower Epidermis

Upper Epidermis

• Top-most layer
• Contains Stomata
• Layer of wax - Waxy Cuticle (NOT A CELLUAR COMPONENT!!!!)
  • Reduces water loss

Mesophyll Layer

• Layer of wax - Waxy Cuticle (NOT A CELLUAR COMPONENT!!!!)
  • Reduces water loss

Palisade Mesophyll

• Elongated
• Tightly packed together
• Has majority of chloroplasts
• Contains vascular bundle, xylem on top, phloem bellow

Spongy Mesophyll

• Rounded cells
• Has more inter celluar air spaces
• Air goes in from stomata to intercelluar air spaces
• Has chloroplasts

Lower Epidermis

• Lowest layer
• Contains Stomata
• Guard cells:
  • Flank stoma
  • Stoma is a hole from space between 2 guard cells
  • Has cell wall of uneven thickness
    • Thicker cell walls near the stomata
    • When water goes in, one side bends more than the other
    • Makes stoma larger
  • Has chloroplasts
    • More Light:
      • Make more glucose
      • Higher concentration of glucose
      • Water potential decreases
      • Water from surrounding cells will enter guard cells via osimosis
      • Cell becomes turgid
      • Stoma becomes bigger
    • Less Light:
      • Make less glucose, net decrease of glucose
      • Lower concentration of glucose
      • Water potential increases
      • Water from guard cell will leave to other surrounding cells via osimosis
      • Cell becomes flaccid
      • Stoma becomes smaller
• Layer of wax - Waxy Cuticle (NOT A CELLUAR COMPONENT!!!!)
  • Reduces water loss

Organelles

Chloroplasts

• Contains chlorophyll
  • Contains magnesium
  • Is green
• Facilitates photosynthesis
• Double membrane organelle
• Inner membrane is folded and stacked
  • Chlorophyll is found in inner membrane
• Chlorophyl captures light energy and converts it into chemical energy
• Chemical energy is stored in chemical bonds of glucose

Transport Structures

Xylem

Structure

• Made of many hollow xylem cells

How it works*

• Transpiration

Functions

• To transport water and dissolved mineral salts from the roots to other parts of the plant
• Provide mechanical support for the plant

Adaptations

• Walls are strengthened with lignin to provide mechanical support
• No end walls and protoplasm
  • Less resistance to the flow of water

Phloem

Common Misconception

Phoem does not transport glucose, but sucrose instead!

Structure

• Made of 2 cells: Companion cell + Sieve tube elements
  • Companion cell is fully living cell
  • Sieve tube element is “half dead, like a zombie”.
• Sieve tube elements have thin layer of cytoplasm inside the tube
• Does not have lignin
• Presence of sieve plates (end walls)
  • Perforated

How it works*

• Companion moves sucrose into the sieve tube via ATP
• Concentration of sucrose in sieve tube increases
• Water potential decreases in the phloem
• Water from xylem moves into phloem via osmosis
• High pressure in phloem
• Pushes sucrose up :D

Functions

• Transport of manufactured food substances (e.g. sucrose and amino acids)

Adaptation

• Companion cells compensate for lack of organelles in the sieve tube elements
  • Contains high levels of mitochondria
  • Increased respiration, which releases more energy for ATP
• Pores in the sieve plates allow sucrose and amino acids to flow through the sieve tubes

Root Hair

Structure

• Thin-walled, tube-like protrusion form an epidermal cell
• Increases SA:V, increases rate of uptake of water

Function

• Selectively permeable plasma membrane
• Many mitochondria

Adaptation

• Prevents cell sap which contains sugars, amino acids and salts from leaking out via diffusion, thus maintaining a lower water potential than soil solution
• Release energy for ATP of mineral salts into cell