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Tissues and the Primary Growth of Stems :smiley: (Concepts (monocots…
Tissues and the Primary Growth of Stems :smiley:
External Organization of Stems
shoot
short shoots
thick fleshly leaves (onions, daffodils, garlic)
bulbs
vertical thick stems
papery leaves (crocus and gladiolus)
corms
stem plus leaves, flowers or buds
nodes
where leaves are attached
region between nodes
internodes
long and thin
stolons
intermediate
wide(asparagus)
narrow (alfalfa sprouts)
trunk
allow the plant to reach brighter light to the top of the forest
stem
arrangement of leaves
phyllotaxy
distichous phyllotaxy
arranged in twos
spiral phyllotaxy
slightly to the side
most common arrangement
decussate phyllotaxy
arranged in
four rows
is an axis
area above where leaf attaches
leaf axil
axillary bud
bud scales
terminal bud
tubers
bulky underground plant organ
mainly a means of storing nutrients (potatoes)
horizontal like rhizomes
grow for short periods
rhizomes
freshly horizontal stems
allow plant to go underground (bamboo, irises, canna lilies)
Basic types of cells and tissues
collenchyma
provides support
layer under epidermis
makes tips resistant to breaking
primary cell wall
thick corners
exhibits plasticity
presenting elongating shoot tips
works with parenchyma
sclerenchyma
primary and secondary wall
prevent protoplast from expanding
develop from parenchyma cells
unlike collenchyma
sclerenchyma supports plant by strength alone
lattertype
fibers
remain alive at maturity
carry out metabolism
elastic secondary walls
strong
wood
branches
sclereids
elastic secondary walls
short
masses of sclereids
shells of coconuts
shells of walnuts
brittle and inflexible
Parenchyma
glandular cells
secrete
mucilage
resins
fragrances
oils
nectar
mass of parenchyma
parenchyma tissue
petals
fruits
soft leaves
conducts nutrients
phloem
seeds
dying at maturity
photosynthesis
chloroenchyma cells
numerous chloroplasts
thin walls
thin walls
transfer cells
short distance transport
ingrowth on inner surface of walls
extensive knobs
ridges
Internal Organization of Stems
vascular Tissues
Xylem
conducting cells (both are sclerenchyma)
vessel elements
entire stack of vessel elements
vessel
only one perforation
provide a way to move water
with less friction than tracheids
produce primary and secondary walls
an entire region of both its missing
die at maturity
hole called periforation
is digested thought primary wall
tracheids
obtain water from tracheids below
pass it on to those above
pit membrane
permeable to water
offers slight resistance
Tracheary elements
reticulate thickening
secondary wall
deposits in shape of a net
stop cell division
becomes long and narrow
secondary wall
reinforces primary wall
scalariform thickening
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annular thickenings
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helical thickening
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circular bordered pits
primary wall is underlain by secondary
pits that allow water movement
are weak points
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occur in plants
Pholem
conducts water to minerals
sieve element
sieve tube members
end wall sieve areas
large sieve pores
sieve plates
controlled by companion cells
prominent nucleaus
dense cytoplasm
filled with ribosomes
smaller
companion cells
loads sugars in and out of sieve tube members
sieve cells
associated with albuminous cells
plasmadesmata enlarge
sieve pores
cluster
sieve areas
nuclei degenerate
cells remain alive
outermost surface of a herbaceous stem
Epidermis
a single layer of parenchyma cells
barrier against invasion by bacteria and fungi
critical function for plants
elongate outward
trichomes
makes it difficult for animals to destroy it
create immobile air
allows water molecules
to bounce back
hair
unicellular
long narrow epidermal cells
shade underlying tissues
multicellular
single row of cells or several cells wide
stoma
guard cells
a pair of cells
stomatal pore
open during daytime
swell by absorbing water
special radial arrangement
human epidermis
much thicker
consists of layers of dead cells
almost always
thin walled parenchyma cells
outer tangential wall
encrusted with cutin
fatty substance
makes wall impeccable water
cutin builds up
cuticle
outside cuticle
layer of wax
indigestible
non-nutritious
plus wax
inhibit entry of carbon dioxide
smooth cuticle
fungal spores count stick
interior of the epidermis
cortex
contain large crystals
calcium oxalate
deposits of silica
angiosperms
large air chambers
buoyancy
complex
containing many cells
secrete latex, mucilage or pitch (resin)
cortex parenchyma is arenchyma
an open tissue with large intercellular airspaces
simple and homogeneous
sometimes collenchyma
composed of photosynthetic parenchyma
Vascular Bundles
arranged in a ring surrounding
the pith
collateral
xylem
primary xylem
pholem
primary pholem
xylem and phloem occur together
vasular bundles
located interior to cortex
Concepts
monocots
lilies
cattails
philodendrons
palms
grasses
basal angiosperms
magnolias
laurels
water lilies
Stems
transport structures
store sugars
produce leaves
hold in sunlight
support structures
water conserving
leaves
angiosperms
largest division in plant kingdom
herb
never gets bark
bromeliads
eudicots
asters
maples
roses
roots
some are rootless
plants become water conserving
roots absorb carbon dioxide
production of critical hormones
plants bodies
two fundamental types
herbaceous
primary plant body
woody body
secondary plant body
Stem Growth and differentiation
exterior cells mature
protophloem
short lived (function for only one day)
cell closest to the metaxylem
metaphloem
large sieve areas
much smaller than cells in metaxylem
apical meristems
sub apical meristems
visible differentiation begins
cells stop dividing
start elongating
fracheids or vessels elements
protoxylem
dead at maturity
longest time of growth
before differentiation
metaxylem
cells divide
by mitosis and cytokinesis
progenitor cells
