3.2: Roots Flashcards
functions of roots
anchorage
absorption
storage
interaction
hormone production
- develops from radicle
- branching lateral/branch roots
taproot
- arises when radicle dies/ after germination
- root primordia at base grows out
fibrous root
extreme tip pushes thorough soil
root tip
- protects root apical meristems
- secrete mucigel
- constantly worn (renewed w parenchyma)
root cap
inc SA
not lateral roots
root hairs
- root epidermis w/o stomata, cuticle
- w/ root hairs
- produces mucigel
rhizodermis (epiblem)
rhizodermal cells; gives rise to root hairs
trichoblast
rhizodermal cells; don’t produce root hairs
atrichoblast
exodermis w heavily sclerified cells
velamen
- benefits plants +microbes
- =ecosystem by attracting bacteria
- bacteria helps plants collect nutrients
mucigel
- site for gravisensing
- w amyloplasts
columella
amyloplasts of columella cells
statoliths
statolith-containing cells of columella cells
statocysts
- contains new cells of roots
- in apex burried under root cap
Root Apical Meristem (RAM)
- reserve for healthy cells (quiescent stage) if damaged
- mitotically inactive region
quiescent center
- root hairs, cuticle
- cortex enlarges
- matured vascular tissues
zone of maturation
- some meristematic activity
- most permeable = diffusion of water
zone of elongation
- support/ground tissues between rhizodermis and vascular tissues
- site of aerenchyma
- storage of starch
root cortex
- innermost cortical layer
- lignin + suberin
- = casparian strip
endodermis
controls type of minerals that enter vascular tissues
lignin + suberin
casparian strip
- parenchyma cells between endodermis and vascular tissues
- formation of lateral roots
pericycle
- where lateral roots form
- swells into cortex->tear endodermis->form root cap emerges
root primordium
- central vascular cylinder of root
- contains xylem, phloem, protophloem, pericycle
stele
“scattered xylem” in ground tissues
monocot stele
atactostele
route of movement:
- between cells
- water only cross
- by root hairs
apoplastic route
route of movement:
- inside cells
- minerals/water cross
- by root hairs
symplastic roots
route of movement:
materials into protoplast of cell -> inward via symplast
transmembrane route
route of movement:
flows in cells of endodermis -> vascular bundles
endodermal route
support root:
plate-like
tall in tropical trees
against wind blow
buttress roots
support root:
for plants subject to powerful water currents
brace roots
support root:
adventitious roots extend to soil
for monocots w wider stems
prop roots
support root:
for epiphytes
along surface of bark
clinging roots
support root:
for figs as epiphytes on host tree
strangling roots
