Please enable JavaScript.
Coggle requires JavaScript to display documents.
Tissues and the Primary Growth of Stems (internal organization of stems:…
Tissues and the Primary Growth of Stems
stem growth and differentiation
cells grow longer by creating new cells at tips in region called apical meristems
region below apical meristems is called subapical meristem
ground meristem=equivalent stages of pith and cortex
epidermis cells differentiate here
protodem=epidermal cells in early stages of differentiation
visible differentiation visible
some stop growing and start elongating
largest tracheary element to grow is metaxylem
outer cells of vascular bundle closest to metaxylem called metaphloem
size difference (larger) than protoxylem
do not have to extensible, feasible secondary wall
must have either annular or helical secondary walls
is called protoxylem
young cells of xylem and phloem called provascular cells
has to be extensible
contain dead cells at maturity
become first trachieds or vessel elements of vascular bundle
also dividing and growing
divide by cytokinesis
divide by mitosis
produce progenitor for rest of plant
internal organization of stems: Arrangement of primary tissues
vascular bundles
are collateral, contain phloem and xylem strand parallel to each other
include xylem and phloem
phloem is called primary phloem and mixed with
may be storage for parenchyma and mechanical sclerenchyma as phloem fibers
sieve elements
or albuminous cells
companion cells
xylem part is called primary xylem, because it is part of primary plant body
distributed as complex system in moncots
in basal angiosperms, eudicots, arranged in ring called pith
epidermis
contain elongated cells that become trichomes or hairs
makes it difficult for animals to land/walk/chew on
outer wall encrusted with cutin
fatty substance that makes wall impermeable to H20 :red_cross:
builds up a more/less pure layer called cuticle
not enough in severe conditions, extra waxy layer added as well
wax and cutin inhibit entry of CO2
contain guard cells with stomatal pore between them
permit entry of CO2
guard cells absorbing H20 and swell, exposing Stoma, allow CO2 to enter
1 more item...
done by
together constitute a stoma
protects against insects and pathogens
protects against bacteria
helps keep water in during uptake or air
outermost surface of plant, one layer of parenchyma cells
exchange of of materials between plant and environment happen here
phloem
2 conducting cells
sieve elements nuclei can die but cell lives on
sieve elements refer to either
sieve tube members
associated with companion cells
load sugars into and out of sieve tubes
evolved same time as the flower
shorter than the plant
end wall sieve pores form sieve plates
small with large ends, stacked end to end
are parenchyma cells, one primary wall
as sieve elements mature, plasmodata in cell develop sieve pores
together form sieve area
sieve cells
associated with albuminous cells
help control cell after nuclei dies
elongate, spindle-shaped and sieve areas all over surface
evolved first, found in fossils
cortex
interior to the epidermis
composed of compacted parenchyma and somtimes collenchyma cells
water based plants have large cortical openings that aid in buoyancy
xylem
2 types of conducting cells
vessel elements
entire stack of vessel elements=vessel
can be meters long
only one perforation
have region missing form walls called perforation
must be adjacent and each element has 2 perforations
have primary and secondary walls
provide water movement with less friction
must absorb water form parenchyma cells, tracheids, or other vessels
both are types of sclerenchyma
tracheids
contain pit-pairs, aligned set=pit membrane
obtain water from other tracheids
tracheary elements with reticulate thickenings, 2nd wall is net shaped
primary wall of parenchyma cells
secondary wall impermeable to H2O
simple version of secondary wall contains
scalariform thickening, provides strength
helical thickenings, exists as 1-3 helices interior to primary wall
annular thickenings which are rings that provide surface area for movement
are weak but primary wall free of 2ndary wall
vascular tissue
for small organisms that are either unicellular or thin sheet of cells that are separated for nutrients by 5-6 layers
two types
xylem
conducts water and minerals
not a circulatory system
nutrients and wasted carried by xylem either used or evaporated, travel through dead cells
phloem
sugars and minerals
pick up sugar where it is abundant, takes to where it is needed
storage organ in summer as well
fruit in summer
flowers
leaves
external organization of stems
types of stems
tubers, horizontal like rhizomes. grow for short period of time
bulbs, short and thick/fleshy leaves
rhizomes, fleshy horizontal stems. allows growth underground
all storage roots are subterrainean
corms=vertical and thick with thin leaves
stolons, also called runners
once it finds suitable microhabitat,
new roots established, resembles new plant
grows shorter and more vertical
are able to explore due to long/thin internodes
arrangement of leaves on a stem= phyllotaxy
spiral phyllotaxy=each leaf is located slightly to the side of ones immediately above and below it, forms a spiral
decussate phyllotaxy= 4 rows
distichous phyllotaxy= 2 rows of leaves
3 or more= whorled
2 leaves=opposite phyllotaxy
one leaf present= alternate phyllotaxy
important so that leaves do not shade each other
shoot=stem plus leaves
stem organization
end of each stem is terminal bud
bud is covered in waxy bud scales, protects leaves
nodes, where leaves are attached :leaves:
leaf axil, point just above stem/leaf attachment
within leaf axil is axillary shoot=miniature shoot
leaf scars left when leaves fall in winter :fallen_leaf:
internodes, region between nodes
stem is an axis
Basic types of cells and tissues
Parenchyme
mass of these cells= parenchyma tissue
phloem conducts nutrients over long distances
some function by dying at maturity
glandular cells
limited chloroplasts
also parenchyma cells
secrete nectar and fragrances
Transfer cells
mediate short distance transportation
chlorenchyma cells and parenchyma cells involved with photosynthesis
many chloroplasts
most common is soft parts of plants
only good for thin walls
relatively inexpensive to make
sclerenchyma
two types of cells
mechanical
fibers
many dead, those alive used for storage
new cells have primary walls, are parenchyma cells
pit-pair is the meeting of 2 pits in secondary wall :hole:
sclereids
more or less isodiameter, often dead at maturity
conducting
vessel elements
short and wide, 1-2 perforations, dead at maturity
tracheids
long and narrow, contain no perforations, dead at maturity
cannot swell do to absorption of water, very rigid
can support plant by itself
develop from parenchyma cells in mature organs
elastic, can be deformed and return to shape
different
has primary wall and thick secondary wall that almost always lignified
collenchyma
can absorb water powerful enough to swell
usually produces in shoot tips
require more glucose
by itself unable to support itself. needs parenchyma cells :<3:
present just under epidermis or bands by vascular bundles
exhibits plasticity
allows plant to form to increase and decrease in pressure or tension, stays in new shape
primary walls thin but thick in some spots (corners)
angiosperms
basal angiosperms
informal classification of flowering plants
monocots
eudicots
body of a herb
herb is a plant that never becomes woody
Primary plant body
secondary plant body
Ancient plants
derived from algae that washed up on shore
2 mutations occured
enhance roots ability to capture CO2 and photosynthesis
stems and leaves conserve more H2O
developed stems and roots
leaves vary in size depending on [climate]
leaves to capture sunlight more effectively
