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Tissues and the Primary Growth of Stems - Coggle Diagram
Tissues and the Primary Growth of Stems
Stem Growth and Differentiation
basic general concepts
differences here are important
most plants are herbs
all primary tissues
no woody stalk
live less than a year
flowering plants are angiosperms
eudicot examples
broadleafs
roses, maples, asters
monocot examples
grasses, cattails, palms
bark is a secondary tissue
Internal Organization of Stems
epidermis
outermost layer
single layer of parenchyma cells
functions in both gas exchange and protection
outer surface coated with cutin
makes wall waterproof
build up=cuticle
stoma
stomatal pore
allows passage into and out of cell
guard cells
close pore when needed
trichomes
"hairs"
protect leaf from animals
alters vapor pressure
cortex
consists of photosynthetic parenchyma
sometimes more advanced
can contain calcium, silica, latex, etc.
deep to epidermis
can be dense or aerenchyma
vascular tissue
xylem
conducts water and minerals
2 types
vessel elements
tracheids
morphological styles
development is similar in both
secondary cell wall=rings
annular thickenings
lots of surface area for water, little strength
secondary cell wall=1-3 helices
helical thickening
secondary cell wall extensive
scalariform
very strong
secondary cell wall like net
reticulate thickening
phloem
one of the important functions
conducts sugars and minerals
2 types of cells
sieve cells
companion cells
brain of the system
sieve tube members
stacks of members->sieve tubes
connections between these=plates
plates have lots of pores, allow materials to flow
internal components gone
2 more items...
transport of materials where diffusion in not sufficient
External Organization of Stems
Basic terms
Shoot
stem, leaves, flowers, buds
Stem
axis
Nodes
where leaf attaches
Leaf Axil
stem area just above leaf attachment point
Bud Scale
small, corky, waxy bud covering
Terminal Bud
bud at the end of a stem
Phyllotaxy
arrangement of leaves on a stem
alternate, opposite, whorled
leaves need to not cover each other
Arrangement of nodes and internodes
important part of shoots
despite smaller size, all plants have these
cabbages have short internodes
leaves stack on each other
vines have long internodes
exploration
Stolons
help exploration
"runners," internodes extra long and thin
leaves do not expand
allow plant to grow without wasting resources
Bulbs
short shoots, thick fleshy leaves
Corms
vertical thick stems, thin papery leaves
Rhizomes
fleshy horizontal stems
plant spreads undergound
Tubers
horizontal, grown for short time as energy storage
The axil of every leaf contains a bud
some buds become flowers
a few buds become branches
resources are often spent on trunk instead
Basic Types of Cells and Tissues
Parenchyma
Types of cells
Chlorenchyma
photosynthesis
thin walls allow gas exchange
other types of colored cells
thin walls allow color to be visible
Glandular
secretion cells
nectar, fragrances, mucus, resins, and oil
large amounts of dictyosomes and ER
intake large amounts of substrate->large amounts of product
Transfer
used in short distance transfer
cells cannot have microvilli to increase SA
have similar structure on
inside
knobs, ridges, and ingrowths
Functioning through death
stamens and some fruits
must be opened
cell dies and is broken down
gas exchange
cells die and middle lamella is broken down
protoplasm converted as cell dies
becomes mucus and "milky latex"
Collections make Phloem
Most prevalent type of cell in the plant
Thin cell wall important to function
Collenchyma
Cell wall is key
similar to clay, able to retain a shape
pressure bends cell wall
cell maintains appearance with force removed
stretchy
useful in shoot tips
Often found below epidermis
Expensive for plant to build
lots of glucose in cell wall
cost only pays off in stem shoot tips
underground is protected by dirt
Sclerenchyma
Primary and Secondary cell wall
Provides stronger, more elastic support
when deformed, returns to original shape
not good for shoot tips
would prevent growth
secondary cell wall often lignified
cannot be expanded by turgor pressure
2 cell types
conducting
mechanical
fibers
long and flexible
trunk of tree, bending of branches
sclereids
short, cuboidal
brittle, masses are like rocks
found in pits
function whether living or dead
plasmodesmata are important
secondary cell wall would kill cell, no passive diffusion
Begin as Parenchyma
differentiate into fiber or sclerid
begin deposition of secondary cell wall
placed inside the cell
internal contents reduced
