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Chapter 6: Leaves (Internal Structures of Foliage Leaves (Epidermis…
Chapter 6: Leaves
Internal Structures of Foliage Leaves
Epidermis
loss of water is transpiration
waterproof
film of water is broken up by trichomes
Cuticle (waterproofing agent)
water loss from stomata is low
Stomata
majority of stomatas are found on lower layer
ventral side has the most if not all stomatas
sunken in eperdermal cavities (crypts)
Trichomes
help supply protection from insects and elements
hair on epidermises
can be posioness
helps protect the plant
Mesophyll
Palisade Parenchyma
contains photosynthetic material
large surface for dissolution
Thickness depends on light intensity
Spongy Mesophyll
lower portion for CO2 diffusion
air spaces for stomata
presence depends on sunlight
ground tissue
Vascular Tissue
Midrib
minor veins
loading sugars
releasing water
lateral veins emerge
conduction
located between mesophyll layers
bundle sheath
means of water transport
bundle sheath extension
Petiole
leaf traces
intermediate between leaf blade and stem
stipules
photosynthesis in some plants
apical meristem protection
Initiation and Development of Leaves
Monocots
apical meristem creates a cylinder
surface doesn't change
volume changes by water
similar to succulent leaves
expansion of shoot to form leaf primordium
imitates some eudicot lamina
no definate size like grass
expansion through leaf sheath base
conduction is never interrupted
constant protoxylem and protophloem stretching
Basal Angiosperms and Eudicots
leaf primordium
midrib and side wings
grows and increases thickness
protoderm cells protrude
lamina expansion
leaf pattern is complete
cells differentiate
Dormant Cells
grow in maturation but not mitosis
Absorb water in the right season
Morphology and anatomy of Other Leaf Types
Modications
Spines
cacti
protective around plant
hardened fibers
Bud Scales
protection around tip
corky bark
close to step with no petiole
Tendrils
coiling from one sided growing
Capable of sensing contact with objects
Types of Leaves
Sclerophyllous Foliage Leaves
high presence of sclerechyma cells
produces a lot of sugars
flexible and edible
succulent leaves
thick and fleshy
volume changes from water
permits desert plants to live
very few air spaces
Conifers
always simple
conifers are examples of simple leaves
needles or scales
Perennial, evergreen
Anatomy
Kranz Anatomy
helps with air enviorments
adapted C4 plants
Insect Traps
altered structures
tubular lamina
permeable epidermis
digest insects for nitrogen
watery digestive fluid
overview
Leaves function with stem
leaves rarely have secondary tissue
stems elevate to get light to leaves
each leaf has specific functions
External Structures of Foliage Leaves
Functions
keep water in and living things out
photosynthesis
thin for light penetration
best for leaves to be flat
also called the lamina
flat part is the leaf blade
compound leaf
flowing water fleaves
mutliple points
leaflets
rachis
attaches to petiolule
do not have buds
shape of leaf protects against incests
simple leaf
less turbulance
one blade
greater percent of photosynthetic material
differ in shape as juvenile to adult
leaf structures
abaxial side or vein backbone
reticulated venation
bundles of vascular tissue
dorsal and ventral sides
have petiole or stalk
petiolate
without it are sessile leaves
mostly monocots
sheathing leaf base
help with wind movement
perpendicular is the abscission zone
forms leaf scars
cuts of leaves when old
proper structure for stability yet cheap
leaf shape
helps with plant identification
variable even in same plant
margin
important in shape
smooth, toothed, lobed, etc.
