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Chapter 7: Roots (Roots (Haustorial Roots (Parasites (adhere firmly to…
Chapter 7: Roots
Roots
Storage Roots
Prop Roots
stabilization
narrow stem transplants
extensive growth thru the air
Aerial Roots
waterproof barrier of dead cells
dangle freely
Contractile Roots
bury
changes depth (contracts)
Haustorial Roots
Parasites
adhere firmly to host
draw nutrients
no soil growth
Strangler Figs
host death
no soil seed germination
Internal Structure
Root Cap
thick layer of cells
mucigel
lube
soil nutrients
cell multiplication
dynamic equilibrium
Root Apical Meristem
localized growth
quiescent center
inactive central region
Zone of Elongation
behind apical
division / expansion
cells enlarge
outer =protoderm
epidermis
permeable tissues
Zone of Maturation
root hairs grow
increase absorption
endodermis
casparian strips
control mineral intake into xylem water stream
impermeable
Mature Portions
root hair
die & degenerate
passage cells
casparian strips
root pressure
water
endodermis maturation
lignin
watertight sheath
Modifications
Nodules
formed by bacteria in infection thread that forms a module after mitosis
aids in use of Nitrogen
Nitrogen Fixation
chem conversion of atmospheric Nitrogen into usable compounds
Mycorrhizae
both organisms benefit
ectomycorhizzal
woody forrest plants
fungal hyphae penetrate between outer root cortex cells (no cell penetration)
endomycorrhizal
herbaceous
penetration of cell (not thru casparian strip)
Functions
Anchor
orientation
absorb
water & minerals
Produce Hormones
cytokinin
gibberellin
External Structure
Organization of Root Systems
NO pith
lateral roots
arise in pericycle
Radicle
embryonic root
taproot
Fibrous root system
similar size roots
radicle death
adventitious roots
increase absorption/transportation
taproot system
ex. carrots
Structure of Individual Roots
root tip
growth
root apical meristem
Origin and Development of Lateral Roots
cell divisions in pericycle
root primordium swells
apical pushes thru endodermis and epidermis
connected
cap protects meristem
connected with bottom
leads to root pressure
