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Chapter 8: Roots - Coggle Diagram
Chapter 8: Roots
Origin and Development of Lateral Roots
initiated by cell division
some densely cytoplasmic with smaller vacuoles
resume mitotic activity
localized activity
root primordial swells into cortex
breaking of endodermis
Concepts
Function
1) Anchoring
2) Absorbing water and minerals
3) Producing Hormones
differ in shape from leaves
active in production
Taproots
carrots, beets, and radishes
main site of carbohydrate storage during winter
Internal Structure of Roots
Root Apical Meristem
in relationship to root tissues
cells originate in meristem and extend
no disruptions
central cells not synthesizing
quiescent center
Zone of Elongation
behind root apical meristem
cells enlarging
no mature cells
tissues permeable
Zone of Maturation/Root Hair Zone
root hair grow
absorption increase
layer of fats
Zone of Elongation merge
endodermis
Casparian Strips
pericycle
Mature Portions of the Roots
root hairs die
occasional Casparian Strips
passage cells
sheath around vascular tissues
root pressure
Other Types of Roots and Root Modification
Storage Roots
long term storage
carbohydrates
summer photosynthesis
roots only permanent organs
used to produce new shoot
Prop Roots
roots grow through air
Palms
: 20 to 50 cm long
Screw Pine
not a pine
monocot
3 to 4 meters long
buttress roots
plate-like
brace trunk from wind
Mycorrhizae
80% of seed plants have symbiotic relationship with soil fungi
both organisms benefit
2 main types
ectomycorrhizal relationship
woody forest plants
fungal hyphae penetrate
never invade cells
endomycorrhizal association
herbaceous plants
penetrated as far as endodermis
cannot pass through Casparian Strips
do not break plasma or vacuole membranes
Root Nodules and Nitrogen Fixation
scarcity of nitrogenous compounds
growth limiting factor
plants can not use N2
Nitrogen Fixation
: chemical conversion
infection thread
Rhizobium
penetrate cells
curly root hair
root nodule formed
External Structure of Roots
Organization of Root Systems
enormous absorptive surface
instead of meters long
highly branched root system
radicle
embryonic root
present in seed after germination
largest root in system
lateral roots
AKA branch roots
carrots for example
may grow more lateral roots
ramified set of roots: highly branched root system
can become swollen
secondary growth
if the plant is perennial or woody
produces wood and bark
fibrous root system
monocot and eudicot
radicules dies during or after germination
root primordia grow and form 1st stages
adventitious roots
plant ages
more primordia initiated in stem tissue
do not come from preexisting roots
are not radicle
increase absorptive and transport capacities
Structure of Individual Roots
root tips
growth in length
growth by discrete apical meristem
localized growth
solid matrix
root cap
thick layer of cells
constantly worn and replaced with new cells
specific structure and growth pattern
cells undergo cell division
