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Chapter 6: Leaves (External Structure of Foliage Leaves (Leaf blade/Lamina…
Chapter 6: Leaves
External Structure of Foliage Leaves
Petiole
stalk
holds blade into light
abscission zone
leaf base
releases enzymes to weaken cell wall
leaf falls
perpendicular to petiole
Veins
bundles of vascular tissue
parallel ventilation
veins are side by side
monocots
reticulate venation
netted pattern
eudicots
angiosperms
distribute water
collecting sugars
Ventral Surface
adaxial/upper side
Leaf blade/Lamina
compound leaf
leaflets
many blades
attached to petiole
#
rachis
extension of petiole
pinnately compund
1 more item...
palmately compund
1 more item...
simple leaf
blade of just one part
Dorsal surface
#
abaxial/lower side
Sessile Leaf
No petiole
sheathing leaf base
Internal Structure of Foliage Leaves
Mesophyll
spongy mesophyll
loose aerenchyma
CO2 diffusion
lower part of leaf
palisade parenchyma
#
main photosynthetic tissue
usually one layer thick
Vascular Tissues
midrib (midvein)
lateral veins
minor veins
releases water from xylem
load sugar into phloem
bundle sheath
fibers around vascular tissue
bundle sheath extension
Epidermis
#
guard cells/trichomes abundant
large surface area
cutin
retain water
transpiration
water loss
protection
stomata
deep into epidermal cavaties
Petiole
stipules
two small flaps
transition between stem & lamina
leaf trances
1,3,5 plus vascular bundles
Morphology and Anatomy of Other Leaf Types
#
Sclerohpyllous Foliage Leaves
limits sclerenchyma
edible
flexible
soft
sclerenchymatous leaves
hardness
resistant
fungi
animals
ultraviolet light
freezing temperatures
foliage must produce more sugars
Leaves of Conifers
sclerophylls
thick cuticle
unpalatable chemical
thick cell walls
simple
flat
scale-like needles
small
Succulent Leaves
thick and fleshy
aizoaceae
ice plant
crassulaceae
kalanchoe
sedum
portulacaceae
portulaca
lewisia
Bud Scales
primarily protective
small and rarely compound
petiole short or absent
tough and waxy
Initiation and Development of Leaves
Basal Angiosperms and Eudicots
shoot apical meristem
leaf primordium
lamina
#
vascular bundles
stomata
petiole
distinct from the midrib
trichomes
cells meristematic
dense cytoplasm and small vacuoles
Monocots
Shoot apical meristem
leaf primordium
hood-like shape
cylindrical primordium
completely encircles apical meristem
Morphology and Anatomy of Other Leaf Types cont'd
Insect Traps
passive traps
incapable of movement
pitcher leaves
active traps
moves during capture
sundew leaves
traps and digests insects
insectivory
obtains nitrogen
Leaves with Kranz Anatomy
lack palisade parenchyma
adapts to dry environments
bundle sheaths
large chlorophyllous cells
C4 photosynthesis
lacks spongy mesophyll
Tendrils
grows indefinitely
can sense contact
doesn't form lamina
grows around the object
Spines
axillary buds
closely packed fibers
no mesophyll parenchyma
needle shaped
no vascular tissue
