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Roots (Other Roots & Modifications (Prop roots Big function of prop…
Roots
Other Roots & Modifications
Contractile roots
Cortex cells contract
Anchors shoot in soil
Mycorrhizae
Ectomycorrhizal relationship
Woody forest plants
Hyphae on outermost root parts
Endomycorrhizal association
Herbaceous plants
Hyphae penetrates root
Invade cortex cells
Provide phosphorous to plant
Form arbuscule
Aerial roots orchids
Epiphytic
Attach to other trees
Roots spread along bark
Velamen (epidermis)
Waterproof barrier
Root nodules
Nitrogen fixation
Symbiotic relationship with
Rhizobium
Rhizobium
enter infection thread
Enter root nodule
Multiply in plant cells
Provide nitrogen
Storage roots
Carbohydrate storage
Biennial species and perennials
Spring brings new shoots
Parastitic flowering plants
Haustorial roots
Adhere to and penetrate host
Contact xylem
Self photosynthesis
Contact xylem and phloem
Little or no photosynthesis
Prop roots
Big function of prop roots
Buttress
Brace trunk against wind
Mangrove prop roots
Brace against currents/tides
Function
Transport nutrients
Extra absorption
Stability
Roots of strangler figs
Grow as epiphytes
Roots grow to soil
Fuse to host's roots
Host tree typically dies
Internal Structure of Roots
Zone of elongation
Cell expansion/enlarging
Closer to root tip
Protoderm
Provascular tissue
Primary xylem
Primary phloem
Farther from root tip
Epidermis
Mature vascular tissue
Metaxylem
Metaphloem
Zone of maturation
Root hair zone
Cortex
Transfer of minerals
Reason Hyphae invade cortex
Apoplastic transport
Symplastic trasnport
Pericycle
Parenchyma cells
Lateral roots initiated here
Endodermis
Casparian strips
Impermeable
Radial walls
Suberin
Lignin
Root apical meristem
Quiescent center
Mitotically inactive
Reserve of healthy cells
Cell division
Root cap
Meristematic cells
Cells in central position
Divided cells pushed forward
Cells on edges
Divided cells grow out
Short lifespan for cells
Soil wears cells away
4 to 5 days
Mature portions of root
Endodermis
Continual application of suberin
Passage cells
Only Casparian strip
Slower to develop
Root pressure built up
Lateral Roots' Origin & Development
Initiated deep within root
Mature pericycle
Initiated by cell division
Mitotic activity
Small root primordium
Root apical meristem
Growth pushes it outward
Emerges through parent root
Differentiates
Connects with parent root
Functions of Roots
Main functions
Producing hormones
Cytokinin
Gibberellin
Anchoring
Stability of plants
Absorbing water and minerals
Cylindrical shape
Additional functions
Carbohydrate storage
Horizontal reproduction
Parasitic attacks
External Structure of Roots
Organization of Root Systems
Taproots
Develop from radicle
Lateral/branch roots
Seen most in eudicots
Fibrous root system
Adventitious roots
"Independent-growing" roots
Seen most in monocots
Structure of Individual roots
Root tip
Root cap
Protects apical meristem
Forced through soil first
Secretes mucigel
Apical meristem
Region of growth (division)
Zone of elongation
Cell division and expansion
Root hair zone
Region of maturation
Root hairs
Aid greatly in absorption
Increases surface area
Reach into small pores
