Chapter 5.  The Root System

• Functions of roots
• Anchorage, absorption, storage, conduction
• The rhizosphere
• Types of root systems
• The embryonic root - radicle (Fig 5.4)
• Tap root systems vs. fibrous root systems (Fig. 5.3)
• Adventitious roots
• Root competition (below ground)
• Root development - the root tip  (Fig. 5.6, 6.7, 5.8)
• Root apical meristem (RAM)
• Root cap
• Primary meristems (protoderm, ground meristem, procambium)
• Root structure - primary tissues (young roots)
• Protoderm develops into epidermis
• Ground meristem develops into cortex
• Parenchyma
• Endodermis - controls access of water and nutrient to xylem
• Procambium develops into vascular tissue
• Xylem "arms" (really ridges, see Fig 5.8)
• Phloem between the arms
• Pericycle - outermost layer of vascular cylinder, retains meristematic function, produces lateral roots, develops into vascular and cork cambiums
• Root structure - secondary tissues (old roots)
• Secondary thickening required to anchor and service growing shoot system in perennial plants
• Vascular cambium - a cylindrical meristem produces secondary xylem (inside) and phloem (outside).  Secondary xylem = wood.
• Cork cambium - produces bark
• Root specializations
• Storage tap roots
• Haustorial roots in parasitic plants
• Mutualisms with nitrogen-fixing bacteria
• Mycorrhizae - mutualisms with fungi