Please enable JavaScript.
Coggle requires JavaScript to display documents.
Ch7: Roots (Other types and modifications (Prop Roots (buttress roots…
Ch7: Roots
Other types and modifications
Storage roots
long term storage
carbohydrates
produce new shoot
biennial species
beets, carrots, celery
only permanent organs
perennials
datura, phlox, daisies
only permanent organs
also store nutrients
do not die
Aerial Roots of Orchids
spread along bark surface
adapted to drought conditions
velamen
composed of dead cell layers
acts as waterproof barrier
doesn't let water leave root
Prop Roots
roots that come out of stems
provide extra stability to plant
do not touch the soil
EX: small palm trees
monocots
buttress roots
large roots on non-stabile trunk
mainly for extra stability
transport water & nutrients
Contractile Roots
thick roots
"contract" and shrink with weather
typically drought
help position plant appropriatly
common in bulbs
Mycorrhizae
relationship between fungi and plants
Ectomycorrhizal relationship
exists in fungal hyphae
slender, threadlike cells
penetrate outermost cortex
do not invade cell
Endomycorrhizal association
in herbaceous plants
branch, form small structure
penetrate cortex cells
Root Nodules and Nitrogen Fixation
nitrogen fixation
nitrogen conversion into usable compounds
root nodule
swelling of root
due to nitrogen fixation
infection thread
rhizobia becomes trapped
Haustorial Roots of Parasitic Flowering Plants
haustoria
roots of parasitic plants
penetrate host plant
connecting to xylem or phloem
inadequate for soil growth
unless rich and moist
Roots of Strangler Figs
seed deposits on branches
roots cling to bark
traveling downward
roots get nutrients from rain
until soil is reached
branch profusely
host tree usually dies
tree cannot photosynthesize
strangler fig "strangle"
Internal Structure
root cap
extra protection for apical meristem
specific structure & growth
apical meristem
contains meristematic cells
quiescent center
a region in apical meristem
allows cell division to resume
zone of elongation
behind root apical meristem
region where cells expand
tissues are permeable
zone of maturation/root hair zone
root hairs grow outward
increases water absorption
merges with zone of elongation
endodermis
innermost layer cells in cortex
usually cylinder shaped
tightly arranged cells
have tangential walls
closest to cortex
Casparian strips
control mineral deposits
in xylem water stream
cells mature into primary tissue
Pericycle
cylinder of parenchyma cells
vital tissue
surrounds xylem and phloem
providing support
provides protection to stem
mature portions of the root
formation of watertight sheath
without epidermis maturation
possible water leakage
may find passage cells
cells containing casparian strips
causes root pressure
powerful absorption of water
water pressure
External Structure
organization root systems
Radical
branch roots
anchor plant
helps water uptake
extends from radical
lateral roots
extends from radical
contributes to water uptake
anchor plant in soil
embryonic part of plant
first part of seedling
fibrous root system
mass of branch roots
adventitious roots
increase
absorptive capacities
transport capacities
structure of individual roots
roots are simple
no leaves
no leaf scars
no auxillary buds
no leaf axils
root cap
thick layer of cells
protects apical meristem
zone of elongation
division
expansion
root hair zone
cells extend
narrow trichomes
root hairs
increase surface area
collect water
collect nutrients
Origin and development of lateral roots
devlopment
small root primordium
moves into root apical meristem
pushes outward
breaks epidermas
creating later root
Origin
initiated by pericycle