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Tissus and the Primary Growth of Stems (primary tissues (epidermis…
Tissus and the Primary Growth of Stems
challenges made plants evolve
spec tissues&organs
2)stems
shoot
=stem w/included leaves
leaf axil
contains
axillary bud
replaces AM if it's killed
mini shoot w/dormant apic.meris.
young leaves
terminal bud
=at extreme tip of each stem
3)roots
1)leaves
attached at
nodes
internodes
=regions between nodes
these can be modified
every plant has:
all 3 share a basic organization
flowering plants (=
angiosperms
)
eudicots
(broad leaves)
monocots
(narrow leaves)
basal angiosperms
3 classes of plant cells:
sclerenchyma
primary wall
thick secondary wall
usually lignified
both are elastic
supports plant by its strength
dead at maturity
2 types: mechanical and conductive
conductive
transport water
tracheary elements of xylem
mechancial
fibers=long, flexible
sclereids=brittle, short, inflexible
collenchyma
thin primary wall
becomes thick in some areas
exists beneath the epidermis
and supporting vascular bundles
parenchyma
masses form parenchyma tissues
stay alive after maturity
active metabolically
thin prim. walls
special parenchyma:
grandular cells
(secrete oils, nectar, etc.)
transfer cells
(short-dist. transport of materials
chlorenchyma
(photosynthetic paren. cells)
phloem
(paren.tiss. conducts stuff long dist.)*
2 plants bodies:
woody
herbaceous
herbs usually annuals
can be monocot/eudicot
phlyllotaxy
alternate
opposite
whorled
primary tissues
epidermis
(forms cuticle)
cuticle prevents gas exchange&dessication
accomplished by
stomata
*trichome
s*
(hairs)
deter herbivory
min. water loss
protect for too much sun
outer walls coated w/
cutin
cortex
interior to epidermis
homogenous
cells typically tightly fitted
vascular tissues
phloem
=distributes sugars&minerals
alive at maturity
sieve tube members
all angiosperms have them
align vertically
sieve plates on each end wall
non-angiosperms don't
controlled by companion cells
sieve cells
elongated,tapered
xylem
=conducts water&minerals
dead at maturity
tracheids
conifers only have tracheids
vessel elements
only angiosperms
pit membranes
organization of vascular bundles
