ROOTS

1
ROOTS

• Absorb water and nutrients
• Anchor plant in soil
• Store carbohydrates/starch

2
Types

• Taproot system

• Fibrous root system

3
Root Adaptations

• Need to adapt to soil env.
• Root cap
• Protects
• Covers apical meristem
• Involved in gravitropism
• Root hairs
• Numerous
• Increase surface area

4
Structure of roots

• Epidermis
• No cuticle in area of root hairs
• Cortex
• Loose parenchyma cells, some sclerenchyma
• Main function is storage
• Large intercelluar spaces
• aeration and water uptake

5
Structure of roots cont.

• Endodermis
• Inner layer of cortex
• Snug fit
• Casparian strip
• Stele
• Vascular cylinder in center
• Outermost layer is pericycle
• Parenchyma cells give rise to lateral roots

6
Movement of Water into the Root

• Root hairs
• Difference in water potential
• 2 pathways water can take
• Symplast
• Apoplast

7
Movement of water cont.

• Most water moves along cell walls, does not enter
  the cell
• Cellulose absorbs water like sponge
• Apoplastic route
• Water and mineral ion diffuse across cortex
• When endodermis reached, waterproof Casparian
  strip prevents further movement along cell walls

8

• http//plantandsoil.unl.edu/croptechnology2005/pag
  es/animationOut.cgi?anim_namewater_movement_roots
  .swf

9
Movement of Water cont.

• Endodermis regulates movement of minerals from
  soil into vascular tissue and throughout the
  plant
• Water enters by osmosis
• Dissolved minerals are actively transported
  against concentration gradient
• Once though endodermal cells, water/minerals
  enter xylem

10
MUTUALISTIC RELATIONSHIPS

• Mycorrhizae
• Soil fungi
• Hyphae increase surface area
• Fungi provide essential nutrients
• Root nodules
• Roots of legumes
• Nitrogen-fixing bacteria
• Atmospheric nitrogen converted to
• ammonia

11
Soil Environment

• 4 main components
• Inorganic mineral particles
• Organic matter
• Water
• Air
• 3 sizes of inorganic particles
• Sand
• Silt
• Clay

12
Soil Environment

• Clay particles
• Negative charge
• Attract positive cations
• Roots pump out H
• Cation exhange occurs at clay
• Positive minerals can be absorbed by roots
• Negative anions tend to wash out of soil

13
Soil Properties affect Plants

• Pore Space
• Equals roughly 50
• Allows air and water to diffuse
• Acidity
• Determines solubility of nutrients
• May lead to leaching of minerals
• Erosion lost fertility