Please enable JavaScript.
Coggle requires JavaScript to display documents.
Tissues and the Primary Growth of Stems (Concepts (stems produce leaves…
Tissues and the Primary Growth of Stems
Concepts
first about 420 years ago ~ algae
no roots, stems, leaves
once landed, specialized tissues and organs evolved
mutations
water ~ transported
supportive tissue ~ necessary
must be able to photosynthesize
stems produce leaves
store sugars and nutrients during winter
means of dispersal
all flowering plants
some rootless
bromeliad family
angiosperms
approx. 297,000 species :<3:
basal angiosperms
waterlilies, magnolias, laurels
eudicots
roses, asters, maples
monocots
grasses, lilies, cattails, palms, philodendrons
primary plant body
herbaceous body
herb
never becomes woody
secondary plant body
woody body
Basic Types of Cells and Tissues
parenchyma
primary walls
remain thin
typically alive at maturity
parenchyma tissue
mass of cells
most common
phloem
soft leaves, petals, fruits, seeds
numerous chloroplasts :<3:
some function by dying
some stamens/flowers must open
when they open, they die
inexpensive to build
Collenchyma
unevenly thickened primary walls
some areas thin, some thick
typically alive at maturity
provide plastic support
can be stretched
present at elongating shoot tips
ex. vining plants like grapes
just under epidermis
works together with parenchyma
CONNECTION!! :!:
need more glucose
Sclerenchyma
both primary wall and think secondary wall :star:
ELASTIC
can be deformed
many dead at maturity
tracheary elements ~ involved in water transport
vascular plants
long/narrow
Mechanical sclerenchyma
sclereids
more or less isodiametric
often dead at maturity
fibers
long
many types are dead, some alive
involved in storage
External Organization of Stems
nodes
leaves attached
internodes
region b/w nodes
Leaf axil
stem area above leaf attachment
has axillary bud
miniature shoot
dormant apical meristem
vegetative bud or floral bud
bud scales
terminal bud
phyllotaxy
leaves arrangement
important to position them
Stolons
long/thin internodes
leaves don't expand
advanced
doesn't use much of plant's nutrients reserve
Bulbs
short shoots
thick, fleshy leaves
onions, garlic, daffodils
Corms
vertical, thick stem
thin, papery leaves
crocus, gladiolus
Rhizomes
fleshy horizontal stems
bamboo, irises, canna lilies
Tubers
like rhizomes
but grow for short time
Internal Organization of Stems
Arrangement of Primary Tissues
Epidermis
outermost surface
single layer of parenchyma
different from human epidermis :red_flag:
plant: interchange of materials b/w it and environment
waterproofing; indigestible by bacteria, fungi, animals
cutin and cuticle
pores and guard cells
Cortex
interior to epidermis
simple/homogenous
photosynthetic parenchyma and sometimes collenchyma
most fit together compactedly
some are open
Vascular Tissues
2 types
xylem
water + minerals
enter thru roots
tracheids and vessel elements
phloem
distributes sugars and minerals
phloem cells ~ living
sieve cells and sieve tube members
not a circulatory system :warning:
Vascular Bundles
xylem and phloem
located interior of cortex
pith
parenchyma region
angiosperms and eudiocots
in monocots
inner part of stems
"scattered"
collteral
xylem + phloem running parallel
primary xylem/primary phloem
Stem Growth and Differentiation
apical meristems
region below apical is subapical
cells are also growing and dividing
subpical
visible differentiation begins
some stop dividing and elongate
constitute first xylem to appear
protoxylem
metaxylem'
cells divide by mitosis and cytokinesis
outer part of vascular bundle
protophloem
metaphloem
Protoderm
epidermal cells in early stage of differentiation
provascular tissues
young xylem and phloem
ground meristem
equivalent stage of pith and cortex
primary tissues
tissues produced by apical meristems
primary growth
results from apical meristem activity
