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Roots, root hairs, root hairs, lateral roots, 1, Taproot is a part of the…
Roots
Other Types of Roots and Root Modifications
Storage Roots
provide long-term storage for carbs
carbs used to produce new shoot
biennials and perennials
roots only permanent organs
root advantages
stable environment
less available as food
Prop Roots
act as stabilizers
transport nutrients and water to the stem
buttress roots
upper side grows more rapidly
brace trunk from being blown over
Aerial Roots of Orchids
roots on surface of bark
root epidermis called velamen
waterproof barrier
Contractile Roots
contraction
caused by changes in shape of cortex cells
keeps stems at proper depths
Mycorrhizae
ectomycorrhizal association
never invade cells themselves
endomycorrhizal association
pass through walls of cortex cells but not Casparian strip
Root Nodules and Nitrogen Fixation
nitrogen fixation
infection thread
bacteria sit in it
root nodule
function for extended periods of time
Haustorial Roots of Parasitic Flowering Plants
haustoria
roots of parasitic plants
adhere firmly to host
inadequate for growth in soil
specific adaptations
Roots of Strangler Figs
grow down trees
seeds deposited by birds
kills host tree
lack of light
Internal Structure of Roots
Root Cap
remain in place
provide protection
constantly regenerating
dynamic equilibrium must be maintained
Root Apical Meristem
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quiescent center
inactive central region
becomes active if root apical meristem is damaged
Zone of Elongation
outermost cells protoderm
tissues quite permeable
not much absorbed, what absorbed is used for root's own growth
Zone of Maturation/ Root Hair Zone
root hairs grow outward
increasing absorption of water and minerals
cortex cells
transfer of minerals from epidermis to vascular tissue
endodermis
cylinder of cortical cells
casparian strips
controls minerals that enter xylem water stream
impermeable
pericycle
lateral roots initiated here
Mature Portions of the Roots
passage cells
only Casparian strip
root pressure
water pressure
Concepts
Roots 3 functions
absorbing water and minerals
producing hormones
cytokininin, gibberellin
anchoring plant
stability
taproots store carbs
External Structures of Roots
Organization of Root Systems
lateral roots or branch roots
produce more lateral roots
taproot
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develops from embryonic root (radicle)
becomes largest root of system
fibrous root system
monocots and eudicots
adventitious root
increase absorption and transport capacities
not limited to monocots, also eudicots
asexual propagation by cuttings
Structure of Individual Roots
fairly simple
root tip region where growth in length occurs
root apical meristem
protected by thick layer of cells called root cap
constantly worn away
dictyosomes
secrete polysaccharide mucigel
zone of elongation
cells undergo division and expansion
root hair zone
narrow trichomes
root hairs
not elongating
increase roots surface area
unicellular, never thick walls, and transitory
Origin and Development of Lateral Roots
Lateral roots
initiated by cell divisions in the pericylce
initiated deep within the root
not on surface
formed in mature regions of the root
lateral root emerges, forms a root cap
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Taproot is a part of the root system that stores carbs
Lateral roots form a root cap
The root apical meristem is both an internal and external part of the root
