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Roots (Other types of roots/modifications (Aerial Roots of Orchids…
Roots
Other types of roots/modifications
Contractile Roots
Grow out then pull in
Base of shoot level with soil
Root Nodules & Nitrogen Fixation
Infection Thread
Bacteria/parasoe
Nitrogen Fixation
Conversion of atmosphere nitrogen
Aerial Roots of Orchids
Epiphytic
Dang Freely in air
adapted to drought conditions
waterproof barrier
Storage Roots
carbohydrates form photosynthesis
produce new shoot in spring
Prop Roots
Mangrove Tree
buttress roots
acts as stablizer
transports water/nutrients to stem
Mycorrhizae
Ectomycorrhizal Relationship
penetrate cortex
never invades the cell
Haustorial Roots of Parasitic Flowering Plants
Parasitic Roots
Burrows down and doesn't let go
Roots of Strangler Figs
Kills tree by stragulation
grows at various angles
roots fuse
Internal Structure of Roots
Zone of Elongation
provascular tissue
Primary xylem
primary phloem
Expanded Cells
Permeable tissue
protoderm
epidermis
Root Apical Meristem
Quiescent Center
more resistant to:
Radiation
Toxic Chemicals
Forms new apical meristem if old ever becomes damaged
Zone of Maturation/Root Hair Zone
Hairs grow outwards
Pericycle
Production of lateral root
Increase in absorbtion:
minerals
water
Transfer from epidermis to vascular tissue
Casparian Strings
Control minerals that enter xylem's water
Mature Portion of Root
Passage Cells
Casparian Strips
Root Pressure
Water/mineral pressure
Root Cap
constant regneration
4-5 days between cell formation and sloughing off
Cells small/meristematic
Develop:
Dense starch grains
endoplasmic reticulum dispelled
detect gravity
Origin and Development of lateral roots
premordium
Endodermis torn/crushed
Cell division
initiated with the root
formed in mature region
Never becomes a flower
initiated with cell division of premordium
External Structure of Roots
Organizations of Root Systems
Lateral Roots
Sprout from taproot
Radicle
beginning of a taproot
dies immediately
Adventitious Root
increases transport and absorption
to not come from pre-existing roots
Monocots/Eudicots
Monocots
Cant undergo secondary growth
cant increase conducting capacity
fibrous root system
similar sized roots
Eudicots
Undergo secondary Growth
increase quantity of health
perineal
Structure of Individual root
root cap
mucigel
Root Hair Zone
Epidermal cells extend
Root Hairs
no thick walls
Part of root that does not elongate
Can enter anywhere
Extract water/mineral
unicellular
Transitory
die/regenerate within 4-5 days
Zone of enlongation
Division/expansion
Absence of
leaf axils, leaves, leaf scars, axillary buds
