Plant Root Flashcards
Functions of roots:
stability and proper orientation
Anchorage
Functions of roots:
cylindrical shape that is ideal for what?
Absorption
Functions of roots:
sink organs; mostly sugars and water
storage
Functions of roots:
mycorrhiza; nutrient exchanges
Interaction with other organisms
Functions of roots:
produce cytokinin and gibberellin imported to the shoot system
Hormone production
Root system:
develops from radicle and emerges with lateral or branching roots; common in eudicots; primary root grows downward
Taproot
Root system:
arises when radicle dies during or immediately after germination; no primary root
Fibrous root
External structures of roots:
extreme tip pushes through soil
Root tip
External structures of roots:
formed by terminal parenchyma, protects RAM, must always be renewed and secretes mucigel for lubrication
Root cap
External structures of roots:
greatly increase root’s surface area, not lateral roots!
Root hairs
External structures of roots:
root epidermis, lack stomata, produces mucigel, no cuticle, with root hairs, NOT root periderm
Rhizodermis/epiblem
Rhizodermal cells:
give rise to root hairs
Trichoblasts
Rhizodermal cells:
do not produce root hairs
Atrichoblasts
Rhizodermal cells:
contains exodermis, with heavily sclerified cells
Velamen
Internal structure of roots:
site of gravisensing, has amyloplasts that settle in response to gravity
Columella
Internal structure of roots:
amyloplasts of columella cells
Statoliths
Internal structure of roots:
statolith-containing cells of columella cells
statocysts
Internal structure of roots:
buried under root cap
Root apical meristem
Internal structure of roots:
can resist radiation and toxic chemicals and act as reserve for healthy cells when root cap is damaged
quiescent center
Internal structures of roots:
enlargement of cells, cells differentiate but don’t mature
Zone of elongation
Internal structures of roots:
three tissues in zone of elongation
Protoderm, ground meristem, procambium
Internal structures of roots:
root hairs grow outward, thin cuticle appears to be present, cortex enlarges to transfer minerals from epidermis to vascular tissues
Zone of maturation
Internal structures of roots:
outer most region
rhizodermis
Internal structures of roots:
ground tissues between rhizodermis and vascular tissues derived from ground meristems
root cortex
Internal structures of roots:
innermost cortical layer with casparia strip
endodermis
Route of transportation:
upatek by hydrophilic walls of rot hairs provide access to apoplasts
Apoplastic route
Route of transportation:
minerals and water cross plasma membrane of root hairs and can enter symplasts
Symplastic route
Route of transportation:
minerals and water move through cell wall and plasma membrane
Transmembrane route
Route of transportation:
water and minerals is stopped by casparian strip
Endomembrane route
Internal structures of roots:
parenchymal cells between endodermis and vascular tissues that give rise to lateral roots
Pericycle
Internal structures of roots:
central vascular cylinder of root and holds vascular bundles, pericylce, and some parenchymal cells.
Stele
Xylem forms solid mass at the center surrounded by phloem; no pith
eudicot stele
First vascular tissues to emerge
Protoxylem and protophloem
Second vascular tissues to emerge
Metaxylem and metaphloem
Xylem and phloem are distributed and scattered in ground tissues ~ atactostele
Monocot stele
Root modification:
found in tropical tree roots, become tall and plate like, braces trunk against wind
Buttress
Root modification:
commonly found in mangroves subjected to strong water currents and provides stability
Brace roots
Root modification:
common in monocots. When stem widens, adventitious roots extend to soil and helps aeration of roots submerged in low-oxygen substrate
Prop roots
Root modification:
attached to branches of trees and sometimes dangling in the air
Clinging roots
Root modification:
perched on branched and rapidly grows, hugging the tree
Strangling/drop roots
Root modification:
Only permanent organ in plant, carbohydrates stored in roots to grow new shots
Food storage
Root modification:
common in desert plants, swollen to store water and pulls plant to soil to protect from over exposure to the sun
Water storage
Root modification:
found in bulbous plants, shoot may be buried because root pulls plant down but keeps plant upright and anchored
Contractile roots
Root modification:
bacteria inside can convert atmospheric Nitrogen into compounds for plant use
Nodular
Root modification:
may possess spines to deter herbivores
Protection
Root modification:
allows root to perform gas exchange, common in mangrove
Aeration
Root modification:
chlorophyllous roots capable of photosynthesis, common in aerated orchid roots
Photosynthesis
Root modification:
adventitious roots that give rise to another plant
Reproduction
Root modification:
penetration of host using haustoria and the fusion of vascular tissues between plant and parasite
Parasitism
Root modification:
symbiotic association where fungus is protected and get sugars and complex molecules for plant
Mychorriza
