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tissues and growth of stems (External organization of stems (phyllotaxy…
tissues and growth of stems
Basic types of cells and tissues
Parenchyma
Parenchyma tissue
mass of parenchyma cells
most common type of cell
thin primary walls
Collenchyma
primary wall
becomes thickened in some areas
requires more glucose
production
exhibits plasticity
produced only
shoot tips
petioles
Sclerenchyma
primary wall
thick secondary wall
always lignified
develop from parenchyma cells
provide elastic support
External organization of stems
nodes
leaves attached
internodes
regions between nodes
leaf axil
where leaf attaches
axillary bud
miniature shoot
dormant apical meristem
vegetative bud
branch
floral bud
group of flowers
several young leaves
bud scales
small, corky, waxy
protection of organs
terminal bud
extreme tip
leaf scars
where leaves were attached
phyllotaxy
arrangement of leaves
don't shade each other
opposite phyllotaxy
two leaves per node
whorled
three or more per node
distichous phyllotaxy
arranged in two rows
decussate phyllotaxy
arranged in four rows
occurs only in some species
spiral phyllotaxy
form spiral up stem
most common arrangement
stolons
runners
internodes
long and thin
doesn't use much nutrients
bulbs
short shoots
thick and fleshy leaves
corms
verticle, thick stems
thin, papery leaves
rhizomes
fleshy, horizontal stems
spread underground
examples
canna lilies
irises
bamboo
tubers
horizontal like rhizomes
grow short period
mainly store nutrients
tuber
means bulky
Internal organization of stems
Epidermis
outermost surface on herbaceous stem
types of chemicals
cutin
waxes
properties
waterproofing
ingestible by
animals
bacteria
fungi
Cortex
interior to epidermis
composed of
photosynthetic parenchyma
collenchyma
Vascular tissues
two types
phloem
distributes
sugars
minerals
xylem
conducts
water
minerals
Xylem
conducting cells
two types
tracheids
sclerenchyma
vessel elements
sclerenchyma
Phloem
conducting cells
two types
sieve cells
parenchyma cells
sieve tube members
parenchyma cells
Vascular bundles
xylem and phloem occur
primary xylem
xylem fibers
primary phloem
phloem fibers
located interior to cortex
all are collateral
contains xylem and phloem strands
strand run parallel
Stem growth and difference
apical meristems
cells divide
mitosis
daughter cells grow to original size
cytokines
subapical meristems
region below apical meristem
cells divide and grow
protoxylem
first xylemt to appear
metaxylem
develop
largest tracheary elements
protophloem
exterior cells
metaphloem
cells closest to metaxylem
