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Ch 6 Leaves (External Structure of Foliage Leaves (leaf blade= lamina…
Ch 6 Leaves
External Structure of Foliage Leaves
obvious function = photosynthesis :sunflower:
nutritious
leaf blade= lamina
flat light-harvesting
dorsal surface
blade's lower side
abaxial side
large veins protrude like back bones
ventral surface
adaxial side
smooth
petiole
stalk
holds blade into light
sessile leaf
long and narrow
simple leaf
one part blade
compound leaf
blade divided into several individual parts
veins
bundles of vascular tissue
parallel venation
veins run side by side
Morphology and Anatomy of Other Leaf Types
Succulent Leaves
desert habitat
leaves are cylindrical or spherical
optimal surface to volume shape
reduced CO2 intake
mesophyll has little air spaces
water loss through stomata
mesophyll transparent
photosynthesis occurs deep
Sclerophyllous Foliage Leaves
must produce more sugars by photosynthesis
could lose energy every time it made a leaf
leaves are soft, flexible, and edible
perennial
leaves could live for two years
sclerophylls
Leaves of Conifers
sclerophylls
THICK
cuticle
epidermis
hypodermis
simple
perennial
Bud Scales
bud scales
most common modifications
form tight layer around stem tip
small
rarely compund
primary role is protection
produce thin layer of corky bark
Spines
modified leaves of auxiliary buds
protection
Tendrils
modified leaf
grow indefinitely
cells are capable of sensing contact with an object
Leaves with Kranz Anatomy
C4 photosynthesis
CO 2 transport
Insect Traps
trap and digest insects
active traps
move during capture
passive traps
incapable of movement
entire leaf blade wraps around insect
Internal Structure of Foliage Leaves
Epidermis
transpiration
water loss through epidermis
must be reasonably water proof
protection
leaves
hairy
Mesophyll
ground tissues interior to the leaf epidermis
palisade parenchyma
upper surface of most leaves
main photosynthetic tissue of most plants
spongy mesophyll
lower portion of leaf
Vascular Tissues
between palisade parenchyma and spongy mesophyll
eudicot
midrib= midvein
bundle sheaths
many fibers become arranged
Petiole
varies in size
transition between stem and lamina
leaf traces
one, three, five or more vascular bundles
different bundles patterns
stipules
two small flaps
protect shoot apical meristem
contribute to photosynthesis
small and die early
Initiation and Development of Leaves
Basal Angiosperm and Eudicots
leaf primordium
cells just interior to protoderm growing outward
extends upward, narrow cone
increases in thickness
bulk of mid rib
Monocots
apical meristem
adjacent to primordium
lamina becomes broad and expanded
can be linear and strapped
constant basal expansion
