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Roots (other types of roots and modifications (roots of strangler figs…
Roots
other types of roots and modifications
roots of strangler figs
roots cling to bark of host tree
grow rapidly downward
hug the tree trunk
months to years roots don't contact soil
penetrate soil rapidly once reached
encase host tree
host tree dies and rots away
strangler fig becomes self supporting tree
contractile roots
roots firmly anchor in soil
stem is pulled downward
root surface become wrinkled
uppermost portions contract
arial roots of orchids
epiphytic
adapted to drought
attach to branches of trees
velamen
root epidermis
water barrier
prop roots
extensive growth through air
may take months to reach ground
once on the ground the transport nutrients
act as stabilizers
buttress roots
plate like
brace trunk
tall
storage roots
carbohydrates
used to produce new shoot in spring
in many perennials
phlox
datura
daisies
in biennial species
beats
carrots
celery
mycorrhizae
symbiotic relationship with fungi
endomyocorrhizal relationship
herbaceous plants
invade the cell
dont break vacuole/ plasma membrane
fungi hyphae penetrate root cortex to caspian strip
ectomyocorrhizal relationship
fungi hyphae penetrate b/t root cortex cells
root nodules and nitrogen fixation
scarcity of nitrogenous compounds in soil
main growth limiting factor
symbiotic relationship
nitrogen fixing bacteria
rhizobium
infection thread
penetrates to root cortex
bacteria enters cytoplasm
proliferates and becomes known as a bacteriods
plant and microbe benefit
root nodule
complex
simple
nitrogen fixation
die and decompose = available to plants
prokaryotes us N2 in the air
internal structure of roots
root cap
meristematic
files of cells push forward
starch grains settle to lower side of cell
detect gravity
simultaneously cells on edge
grow towards the side
proliferate
root apical meristem
quiescent center
believed to be a reserve for healthy cells
resistant to harmful agents
mitotically inactive
if apical meristem/ root cap damage
form new apical meristem
quiescent center cells become active
zone of elongation
differentiation
pro-vascular tissue
primary xylem/ phloem
ground tisse
root cortex
protoderm
epidermis
cells expand greatly
cells enlarge
zone of maturation/ root hair zone
root hairs grow outward
increase water absorption
endoderm
tangenital walls
makes endodermis waterproof
incrusted with lignin and suberin
known as Casparian strips
control minerals that enter xylem water stream
pericycle
initiate lateral roots
between vascular tissue and endodermis
mature portions of the root
passage cells
only casparian strips
suspected slow development
root pressure
external structure of roots
organization of root systems
highly branched root system
branch roots
lateral roots
taproot
develops from radicle
embryonic root
turnips
carrots
beets
enormous absorptive surface
fibrous root system
mostly monocots
a few eudicots
adventitious roots
increase absorptive and transport capacities
structure of individual roots
no leaf scars
no leaves
root tip is region of growth
apical meristem
thick layer of cells
protected by root cap
secretes mucigel
lubricates root through soil
rich in carbohyderates
rich in amino acids
release nutrients from soil
foster rapid growth of bacteria
constantly worn away
renewed by cell multiplication
zone of elongation
cells undergo division and expansion
just behind apical meristem
root hair zone
behind zone of elongation
epidermal cells extend out
narrow trichomes
root hairs
greatly increases surface area
form where root is not elongating
penetrate small pores in soil
no leaf axils
no auxiliary buds
origin and development of lateral roots
initiated by cell division in pericycle
small root primordium
organizes into root apical meristem
pushes outward
breaking through endodermis
forms root cap
protoxylem/ protophloem differentiate
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how these begin
