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Chapter 5: Tissues and the Primary Growth of Stems (Basic Types of Cells…
Chapter 5: Tissues and the Primary Growth of Stems
Basic Types of Cells and Tissues
Parenchyma
have thin, primary walls
have the most common cell and tissue in soft plants
examples
chlorenchyma cells
glandular cells
transfer cells
some do function by dying at maturity
stamen
some fruits (i.e. pea pods)
conducts nutrients over long distances
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typically alive at maturity
Sclerenchyma
primary and secondary walls
many dead at maturity
provide elastic support
involved in water transport
two types
conducting
tracheids
vessel elements
mechanical
sclereids
fibers
Collenchyma
uneven primary walls
provide plastic support
typically alive at maturity
thick cell walls
require more glucose for production
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Internal Organization of Stems
Epidermis
contains
stoma
guard cells
stomatal pore
cuticle
cutin
elongate to form trichomes/hairs
Cortex
simple and homogenous
composed of parenchyma and collenchyma
can secrete latex, mucilage, and pitch
Vascular Tissue
Xylem
conducting cells
traechery elements
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vessel elements
circular bordered pits
tracheids
primary wall
must have uncovered parts for water transport
secondary wall
impermeable to water
has thickening to provide support to the primary wall
scalariform thickening
reticulate thickening
helical thickening
Phloem
conducting cells
sieve element
sieve cells
long and narrow
distributed sieve areas
pointed ends
albuminous cells
all nonangiosperm vascular plants
sieve tube members
short and wide
large sieve areas on side and end walls
flat ends
companion cells
angiosperms only
Vascular Bundles
surround the pith
located interior to the cortex
collateral xylem and phloem strands
Stem Growth and Differentiation
apical meristem
grows by cell division
subapical meristem
visible differentiation begins
metaxylem
only differentiate after surrounding cels have stopped elongating
largest tracheary element
protoxylem
dead at maturity
primary walls are glued to elongating cells around them
in vascular bundle
exterior cells
mature as protophloem
can never become differentiated
cells closest to the metaxylem
become metaphloem
can differentiate fully
External Organization of Stems
organization
nodes
internodes
wide
asparagus
intermediate
narrow
alfalfa sprouts
bud scales
terminal bud
leaf axil
axillary bud
apical meristem
miniature shoot
stem examples
bulbs
short shoots
thick, fleshy leaves
examples
onions
garlic
daffodils
corms
thin, papery leaves
examples
crocus
gladiolus
vertical, thick
rhizomes
fleshy, horizontal
allow a plant to spread underground
examples
irises :
canna lilies
bamboo
tubers
horizontal
grow for a short period
example
potatoes
Phyllotaxy
decussate
whorled
opposite
spiral
alternate
distichous
