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Tissues and the Primary Growth of Stems (External organization of stems #,…
Tissues and the Primary Growth of Stems
Types of tissues and cells
Parenchyma cells
#
mass forms parenchyma tissues
Chlorenchyma cells
involve in photosynthesis
numerous amount of chloroplasts
thin cell walls
allows light and carbon dioxide to pass through readily
Glandular cells
secretion includes
nectar
fragnance
mucilage
resins
oil
contain large amount of dictysomes and endoplasmic recticulum
metabolize sugar and minerals
Transfer cells
large, extensive plasma membrane
used for short distance transport
contains numerous molecular pumps
have extensive knobs, ridges and other inner growths
increases surface area
some dies at maturity to function
may create openings to release pollen or seeds
form spaces to allow diffusion of gases within leaves
thin primary cell wall
inexpensive metabolically
Collenchyma cells
primary cell wall
thin in some areas
thick in other, especially in corner
require more glucose for their production
exhibits plasticity
ability to form and deform by pressure and tension
present in shoot tips of vining plants
layer under epidermis or band next to vascular bundles
Parenchyma cells in inner tissue provide support
prevalent in shoot tips and petioles
image
Sclerenchyma cells
cell wall
thin primary and thick secondary
elastic
deform but return to original state if pressure is released
develop from parenchyma cells in mature organs
supports the plant by its strength
conducting sclerenchyma
tracheids
long and narrow with tapered ends, no perforations
dead at maturity
found in all vascular plants
vessel elements
short, wide and have perpendicular walls
found mostly flowering plants
mechanical sclerenchyma
long fibers
more flexible
found in areas where strength and flexibility is required
prevalent in wood of the most flowering plants
short sclereids
isodiometric
brittle and inflexible
mass forms
shells walnuts and coconuts
"pits" or "stone" of cherries and peaches
External organization of stems
#
nodes
leaves are attached
internodes
region between nodes
leaf axil
stem area above where the leaf attaches
axillary bud
miniature shoot with young leaves
covered with bud scales
terminal bud
extreme tip of the each stem
phyllotaxy
arrangement of the leaves in the stem
alternate phyllotaxy
one leaf on each node
opposite phyllotaxy
two leaves per node
whorled phyllotaxy
three or more leaves per node
distichous phyllotaxy
leaves arranged in two rows
corn, irises
decussate phyllotaxy
leaves arranged in four rows
occurs in species with opposite leaves
spiral phyllotaxy
leaves located at side
form spiral up the stem
Shoots
arrangement of nodes and internodes
vines
long internodes
lettuce, cabbage
short internodes
tightly packed leaves
asparagus
wide internodes
sprouts
narrow
stallons
runner
long and thin internodes
leaves do not expand
allows it to expand without much energy
Bulbs
short shoot with thick fleshy leaves
onions, garlic
corms
thick stems with thin peppery leaves
crocus
Internal organization of stems
epidermis
#
outermost layer
single layer of living parenchyma cells
fuctions
prevent water loss in land plants
barrier against bacterial invasion, fungi and insects
protects plants from overheating in bright sunlight
cutin
fatty substance
makes the wall impermeable to water
builds up cuticle
resist digestive enzymes
defense against pathogens
stoma
guard cells
stomatal pore
opens during daytime
provides passage for carbon dioxide
trichomes
hair
elongate outwards
makes it hard for animal to chew on leaves
cortex
interior of epidermis
simple in many plants
contains photosynthetic parenchyma
collenchyma
complex
contains specialized cells
compact and tightly packed cells in most plants
aerenchyma
occurs in fleshy stems
open tissue w/ large intercellular spaces
vascular tissues
xylem
conducts water and minerals
two types of conducting cells
tracheids
thin, narrow
vessel elements
wide
efficient in transporting water
tracheary elements
secondary cell wall
phloem
distributes sugar and minerals
sieve tube members
precursor= sieve cells
stay alive to function
companion cells
control sieve tube members
load sugars in and out of sieve tube members
Stem growth and differentiation
Apical meristem
provascular tissue
primary xylem
primary phloem
fasicular cambium
vascular cambium
secondary xylem
secondary phloem
ground meristem
pith
interfascular cambium
cortex
cork cambium
protoderm
epidermis
cork cambian
cork
phelloderm
cell division by mitosis and cytokinesis
sub apical meristem
visible differentiation begin
elongation and differentiation
protoxylem
metaxylem
longest time for growth before differentiation
protophloem
cells closest to metaxylem
metaphloem
mature exterior cells
similar types connection
categorization connection
functional connection