1. Roots

2. Do not move
More than ½ of plants resources go into roots
Can account for 80% of biomass
Move nutrients into food chain

3. Kinds of Roots: Taproot Fibrous Roots Radicle Main taproot (dicots)
Branch roots
Taproot system
Fibrous Roots
Mostly monocots
Extensive root network
Adventitious roots

4. Function and Structure of Roots
Functions:
(1) Anchorage
(2) Storage
(3) Absorption
(4) Conduction
Structure:
Root Tip = root apical meristem
Root Cap
Sub-apical Region
Zone of cellular division
Zone of cellular elongation
Zone of cellular maturation
Mature Region = primary tissues

5. Layers of Root: Superficial to Deep
Epidermis
One cell thick with thin or no cuticle
Covers all, but not root cap
Lack stomata, have root hairs
Cortex
Composed of ground tissue
Largest part of root
Consists of three concentric layers

6. Cortex continued: Hypodermis Storage Parenchyma Endodermis Suberized
Store starch, many cells, very thick
Lots of intercellular spaces
Endodermis
Cells very tight together
No spaces
Cylinder all through root
Contains Casparian Strip = composed of lignin and suberin

7. Casparian Strip Blocks water and nutrient movement
Material must pass through cells of endodermis to reach vascular tissues

8. Stele Pericycle Vascular Tissue (see later) Pith
All tissues inside cortex, within endodermis
Three types
Pericycle
Meristematic
Forms lateral branch roots that form endogenously
Vascular Tissue (see later)
Pith

9. Root Vascular Tissues Protostelic Siphonostelic
Lobed solid core of xylem
Phloem in notches
Most dicots
Siphonostelic
Tissues form rings
Xylem and phloem alternate
Most monocots, some dicots

10. Factors Controlling Root Growth and Dispursement:
Temperature
Light
Gravity
Soil chemistry
Genetics
Other organisms
Root – Soil Interface

11. Economic Importance of Roots
Modified Roots
Storage
Propagation
Aeration
Movement
Nutrition
Parasitism
Mycorrhizae
Nodules
Aerial roots
Economic Importance of Roots

12. Monocot Stem Cross Section
Lack vascular cambium in mature forms. Vascular bundles embedded throughout tissue.