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Tissues and the primary growth of stems (stem growth and differentiation…
Tissues and the primary growth of stems
Basic types of cells and tissue
parenchyma
most common
have only thin primary walls
soft parts of plants
subtypes
chlorenchyma
involved in photosynthesis
numerous chloroplasts
glandular
secrete nectar, fragrances, mucilage, and resin.
few chloroplast
have lots of dictyosomes and ER
transfer
mediate short distance transport
hold numerous molecular pumps
increase surface area
some function by dying at maturity
release pollen or seeds
cells that conducts nutrients over long distance
Phloem
little glucose is needed to build
collenchyma
thin is some areas thick in others (cell wall)
plasticity
vining plants
unable to hold up stem
works like air pressure in a tire
require more glucose
short tips
young petioles
sclerenchyma
has primary and secondary wall
elastic
wind, animals can damage
prevent protoplast from expanding
conducting sclerenchyma
elastic walls
mechanical sclerenchyma
divided into long fibers
elastic walls
sclereids
develop from cells produced by cell division
short
brittle inflexible
store starch or crystals of oxalate
pit pair
external organization of stems
nodes
where leaves are attached
internodes
between nodes
leaf axil
where leaf attaches
phyllotaxy
arrangement of leaves on stems
no shading
stolens
long and thin internodes
leaves don't expand
bulbs
thick fleshy leaves
tubers
horizontal
distichous
two rows
corn
decussate
four rows
opposite leaves
spiral
leaves are spiraling
internal organization of stems
epidermis
cuticle
acts as defense
inhibits entry of CO2
stoma
pores open
letting CO2 in
guard cells help
trichomes
hairs
elongate outward
layer of immobile air
cortex
can be simple and complex
secrete latex and resin
vascular tissues
xylem
conducts water and minerals
tracheilds
long narrow
ends pointed
vessel element
short wide
ends flat
phloem
distributes minerals and sugars
sieve cells
elongated and spindle shaped
albuminous
sieve tube members
large and wide
companion cells
nuclei degenerate but cells stay alive
sieve cells and tube
vascular bundles
interior to cortex
collateral
stem growth and differentiation
stem cells
apical meristems
mitosis and cytokinesis
sub apical meristem
visible differentiation
first xylem to appear
protaoxylem
metaxylem
meta-golem
differentiate fully
smaller
protophloem
short lived
not differentiated
small cells
protoderm
early stages of differentiation
young cells of phloem and xylem
pro vascular tissues
ground meristem
stages of pith and cortex
primary tissues
tissues produced by apical meristems
primary growth
growth and tissue formation the results from apical meristem