Please enable JavaScript.
Coggle requires JavaScript to display documents.
Tissues & Primary Growth of Stems (internal organization of stems…
Tissues & Primary Growth of Stems
angiosperms
groups of 297,000 species of flowering plants
diversified into several other groups
basal angiosperms
ex: water lilies, magnolias, & laurels
eudicots
broadleaf plants ex: roses, maples, & others
monocots
ex: grasses, lilies, palms, & others
body types
primary plant body
herbaceous
beans, corn & wheat
often live for less than a year but can live for many years (ex: lilies & irises)
tissues are primary tissues
these are herbs
secondary plant body
woody body
trees & shrubs (maples, oaks, roses)
wood & bark are secondary tissues
plant cells
parenchyma
parenchyma cells
only have primary walls that are thin
parenchyma tissue
most common type of cell & tissue constituting all soft parts of a plant
soft leaves, petals, fruits, & seeds are composed almost completely of parenchyma
chlorenchyma cells
are parenchyma cells involved in photosynthesis
glandular cells
that secrete nectar, fragrance, resins, mucilage, and oils are parenchyma cells
transfer cells
parenchyma cells that mediate short distance transport of material by means of a large, extensive plasma membrane
little glucose is needed to build these cells
sclerenchyma
have both a primary wall & thick secondary wall that is almost always lignified (elastic cells)
sclerenchyma cells develop from parenchyma cells in mature organs after they have stopped growing & received their proper size & shape
cells are strong enough to prevent the protoplast from expanding
mechanical sclerenchyma
subdivided into long fibers & short sclereids (both have elastic secondary walls)
fibers
long & flexible most often found in areas where strength & flexibility are important (flowering plant branches)
sclereids
short & cuboidal. Masses form hard & impenetrable surfaces (ex: shell of a walnut)
collenchyma
primary walls are thin but become thicker in some areas
exhibits plasticity, the ability to be deformed by pressure/ tension, & to retain the shape even if the pressure/ tension is released
cells are present in elongated shoot tips that must be long & flexible (ex: grape vines)
external organization of stems
nodes
where leaves are attached
internodes
regions between nodes
leaf axil
just above the point where a leaf attaches
axillary bud
a miniature shoot w/ dormant apical meristem & several young leaves (found within leaf axil)
bud scales
small, corky, waxy covering of a bud that protects the organs inside
terminal bud
at the extreme tip of each stem
phyllotaxy
arrangement of leaves on the stem
alternate
one leave per node
opposite
two leaves per node
decussate
leaves located in four rows
whorled
3-4 leaves per node
spiral
leaves not aligned w/ their nearest neighbors
distichous
leaves located in 2 rows only
stolon
horizontal plant stem that takes root at points along its length to form new plants
bulbs
short shoot w/ thick fleshy leaves (onions, daffodils, garlic)
corms
vertical, thick stems w/ thin papery leaves
rhizomes
fleshy horizontal stems that allow plants to spread underground (bamboo, irises & lilies)
tubers
horizontal like rhizomes, but they only grow for a short period of time & mainly a means of storing nutients
trunk
vertical main shoot that allows plants to reach brighter light in the top of a forest canopy
protophloem
exterior cells mature as this
metaphloem
cells closest to the metaxylem become this
internal organization of stems
epidermis
outermost surface of a herbaceous stem, made of a single layer of living parenchyma cells
all interchange of material between a plant and its environment occurs by means of its epidermis
cutin
fatty substance that encrusts the outer tangential wall to make it impermeable to water
cuticle
cutin build up as a more or less pure layer
a wax layer may be present outside the cuticle; cutin & wax resist digestive enzymes & provide defense against pathogens
guard cells
pair of cells within the epidermis that swell by absorbing water
stomatal pore
hole between guard cells that open during the daytime to allow CO2 to enter the plant
stoma
made up of the guard cells & stomatal pore
trichomes (hairs)
some epidermal cells elongate outward to become this
cortex
interior to epidermis in most plants cells fit together compactly, but in some plants it is an open tissue w/ large intercellular air spaces
vascular tissues
xylem
conducts water & minerals
tracheids
conducting cells (type of sclerenchyma cells)
vessel elements
conducting cells (type of sclerenchyma cells)
phloem
distributes sugars & minerals
annular thickenings
small amount of secondary wall, organized as a set of rings on the interior face of the primary wall
helical thickening
supports primary wall due to water movement by preventing it from collapsing inward
scalariform thickening
provides much more strength
reticulate thickening
secondary wall is deposited in the shape of a net
circular bordered pits
most derived & strongest tracheary elements
border
reduces weakness around the pit
pit membrane
between the primary wall & middle lamella
perforation
large hole digested through a site in the primary wall, often removing the entire end wall
vessel
entire sack of vessel elements
phloem
sieve cell
parenchyma cells; only have primary walls & must stay alive in order to conduct
sieve pores
plasmodesmata enlarge to a diameter > 1 micrometer
sieve areas
clustered sieve pores
sieve tube
cells stacked end to end w/ large sieve areas aligned
sieve plates
end wall sieve areas with large sieve pores
albuminous cells
associated w/ sieve cell
companion cells
sieve tube members are controlled by these cells
sieve tube members
parenchyma cells; only have primary walls & must stay alive in order to conduct
vascular bundles
xylem & phloem together
pith
a region of parenchyma similar to the cortex
collateral
xylem & phloem strands run parallel to each other
primary xylem
of vascular bundle is part of the primary plant body
primary phloem
storage parenchyma & mechanical sclerenchyma as phloem fiber usually but phloem sclereids occur too
stem growth & differentiation
apical meristems
region where new cells occurs
subapical meristem
just below apical meristem where cells divide & grow
protoxylem
where first xylem appears
metaxylem
largest tracheary element of all
protoderm
refers to epidermal cells that are in the early stages of differentiation
provascular tissues
young cells of xylem & phloem
ground meristem
young cell stages of pith & cortex
primary tissues
tissues produced by apical meristems
primary growth
growth & tissue formation that results from apical meristem activity
