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CH 6 Leaves (External Structure of Foliage Leaves (No entry allowed (fungi…
CH 6 Leaves
External Structure of Foliage Leaves
Photosynthesis
Leaves absorb CO2
Converts to carbohydrates
light energy
flat and wide leaf
thin leaf
thick layer of chlorenchyma
Leaf blade (lamina)
flat
light-harvesting portion
Dorsal surface
blade's lower side
Abaxial side
large veins portrude
Ventral surface
upper side
adaxial
smooth
Petiole
aka stalk
holds blade to light
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long, thin, flexible
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no petiole
2 more items...
aka petiolate
Compound
divided, individual parts
leaflets
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palmately compound
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pinnately compound
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Simple
just one part
deeply lobed
one dominant midrib
Prevents water loss
No entry allowed
fungi
bacteria
epifoliar algae
Cannot be delicious/nutritious
Must be cheap
Cannot be sails
Internal Structure of Foliage Leaves
Epidermis
Transpiration
water loss
must be translucent
allows CO2 in
must be waterproof
allows CO2 in
flat, tubular epidermal cells
guard cells
trichomes
glandular
secrete stinging compounds
prevents animals from eating
makes chewing difficult for insects
protects leaf-borne insects
non glandular
provide shade
prevent rapid air movement
slow water loss
Stomata
greater in lower epidermis
rarely any in upper epidermis
Cutin
retain water
make digestion difficult for fungi
prevents spores from sticking
allows spores to be washed off
Mesophyll
ground tissues
interior to epidermis
palisade parenchyma
main photosynthetic tissue
one layer thick
intense light 3-4 layers thick
spongy mesophyll
open, loose aerenchyma
permits CO2 to diffuse
Vascular tissues
midrib (midvein)
lateral veins
minor veins
releasing water from xylem
loading sugar in phloem
must have large surface area
bundle sheath
many fibers
difficult for insects to chew
Petiole
transition between stem & lamina
leaf traces
vascular bundles
stipules
protect apical meristem
photosynthesis
usually die early
https://www.sciencedirect.com/topics/immunology-and-microbiology/petiole
Morphology & Anatomy of Other Lead Types
Succulent Leaves
Crassulaceae
Portulacaceae
Aizoaceae
thick and fleshy
Surface-to-volume
cylindrical
spherical
Water conservation
mesophyll
few air spaces
reduce surface area
water loss through stomata
more transparent
light penetrates further
Succulent Plants
Sclerophyllous Folliage Leaves
photosynthesis
produce more sugars
limited sclerenchyma
soft, flexible, edible
perennial
feasible
resistant to animals
fungi
freezing temperatures
UV light
extended lifetime
prolonged productivity
cuticle
very thick
was abundant on leaves
Leaves of Conifers
sclerophylls
thick cuticle
epidermis & hypodermis have thick walls
contain upalatable chemicals
always simple
few forms
needles
pines
firs
spruces
mostly perennial
evergreens
bristlecone pine
juniper
Initiation and Development of Leaves
Basal Angiosperms & Eudicots
leaf primordium
protrusion that extends upwards
increases thickness
initiates lamina
midrib
2 small, thin wings
meristematic
enlarge lamina rapidly
grows rapidly
taller than apical meristem
consists of protoderm & ground meristem
cells are meristematic
dense cytoplasm
small vacuoles
https://www.pnas.org/content/98/20/10981
Leaf Primordium
Monocots
initiated by apical meristem cells
form leaf primordium
#
lamina
becomes broad
in this