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Chapter 5: Tissues and the Primary Growth of Stems, Cross Conection:…
Chapter 5: Tissues and the Primary Growth of Stems
External Organization of Stems
Nodes
leaves are attached
internodes between
Leaf axil
above nodes
axilliary bud within
either
vegetative
floral
covered by bud scales
Terminal bud
located at extreme tip of each stem
Phyllotaxy
arrangement of leaves
arranged in
alternate
opposite
whorled
distichous
decussate
spiral
Stolons
AKA runners
ability to "explore"
Bulbs
short shoots
thick, fleshy leaves
Corms
Vertical, thick stems
thin, papery leaves
Rhizomes
Fleshy, horizontal stems
allow underground spread
Tubers
horizontal
grow for short period
Concepts
Stem Function
Transport
Support
Additional Roles
Storage
Growth of leaves
Mutations
Enhance water conservation
Leaves
Stems
enhance CO2 absorption and photosynthetic ability
roots
Angiosperms
Flowering plants
Largest division in plant kingdom
Diversified into
Basal angiosperms
Eudicots
Monocots
Fundamental types of plant bodies
Primary plant body
Secondary plant body
Basic Types of Cells and Tissues
Sclerenchyma
#
Has a thick secondary wall
contains pits and pit-pairs
elasticity
develop from parenchyma in mature organs
support
two types
conducting sclerenchyma
mechanical sclerenchyma
subdivided into
fibers
strong
flexible
scleroids
act as brittle and inflexible
create hard, impenetrable surfaces
Collenchyma
primary wall becomes thickened in areas
exhibits plasticity
works with parenchyma to provide support
Parenchyma
#
Primary walls that remain thin
Make up Parenchyma tissue
Most common cell and tissue
Chlorenchyma
involved in photosynthesis
contain numerous chloroplasts
Glandular cells
secrete
nectar
fragrances
mucilage
resins
oils
Elevated amounts of
dictyosomes
endoplasmic reticulum
involved in metabolic functions
Transfer cells
mediate short-distance transport
capable of large-scale molecular pumping
Some cells die at maturity to
release pollen/seeds
create air spaces
convert into mucilage/milky latex
Internal Organization of Stems
Arrangement of Primary Tissues
Vascular Tissues
two types
Xylem
conducts
water
minerals
Phloem
distributes
sugars
minerals
Xylem
"tracheary elements"
tracheids
vessel elements
entire stack is called a vessel
annular thickenings
arranged as rings
small amount of secondary wall
Helical thickening
secondary wall exists as 1-3 helices
Scalariform thickening
Provides more strength
secondary wall
Reticulate thickening
secondary wall in shape of a net
Circular bordered pit
strongest and most derived tracheary elements
weakness reduced by border
Pit membrane
set of
Primary walls
Middle lamella
Perforation
large hole
digested through particular site of primary wall
Cortex
can be simple or complex
Most fit together compactly
some contain large air spaces
Phloem
two types conducting cells (sieve elements)
sieve cells
associated with albuminous cells
sieve tube members
form sieve tube when stacked
controlled by companion cells
Sieve areas
groups of sieve pores
End wall sieve areas form sieve plates
Epidermis
#
Outermost surface of herbaceous stem
single layer of living parenchyma
prevents water loss
provides barrier to
bacteria
fungus
small insects
shields internal cells
Encrusted in cutin
fatty substance
makes wall impermeable to water
builds up to form cuticle
contains guard cells
creates stoma when with stomatal pore
allows opening of stomatal pore
Elongate to become trichomes
AKA hairs
make it difficult for animals to take advantage of plant
shade underlying tissues
creates layer of immobile air next to leaf surface
Vascular Bundles
Phloem and xylem together
interior to the cortex
arranged in one ring surrounding the pith
collateral
primary xylem
primary phloem
Stem Growth and Differentiation
apical meristems
cells divide by mitosis and cytokinesis
produces progenitor cells for rest of stem
subapical meristem
region just below apical meristem
cells divide and grow
produces cells for region below
visible differentiation begins
protoxylem
cells constituting first xylem
oldest develop into metaxylem
protophloem
identical to metaphloem
exterior cell as they mature
metaphloem
identical to protophloem
cells closest to metaxylem
protoderm
epidermal tissue in early stages of differentiation
Provascular tissues
Young cells of
Xylem
Phloem
Ground meristem
young cells of
pith
cortex
Primary tissue
produced by apical meristem
Primary growth
growth and tissue formation
results from apical meristem activity
Cross Conection: Sclerenchyma develop from Parenchyma
Cross Connection: Phloem are made from parenchyma cells
Cross Connection: Cortex is just interior to epidermis
