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Chapter 6: Leaves (Morphology & Anatomy of Other Leaf Types (Spines…
Chapter 6: Leaves
Morphology & Anatomy of Other Leaf Types
Succulent Leaves
thick and fleshy
ex.
Aizoaceae
Portulacaceae
Crassulaceae
Sclerophyllous Foliage Leaves
produce more photosynthesis
ex.
Agave
barberry
Yucca
soft, flexible, edible
Bud Scales
form tight layer around stem tip
protect plant from
low temperatures
wind
Leaves of Conifers
ex
firs
spruces
pine
sclerophylls
thick cuticle, epidermis/hypodermis walls
Spines
ex.
cactus
modified leaves of axillary buds
no mesophyll parenchyma
no vascular tissue
Tendrils
grow indefinitely
cells that sense contact
ex.
cucumbers
squash
peas
if touches, that side stops growing
Insect Traps
ex.
Dionaea musxipula
Drosera
Nepenthes
Sarracenia
ability to trap & digest insects
foliage leaves
parenchymatous
Leaves with Kranz Anatomy
C4 photosynthesis
lack
spongy mesophyll
palisade parenchyma mesophyll
have prominent bundle sheaths
Structure of Foliage Leaves
External structure
Function
Photosynthesis
Storage of water
no entry of fungi, bacteria, algae
cheap
non efficient sails
no taste
leaf blade
flat
light harvesting portion
dorsal surface
blades lower side
large veins like backbones
ventral surface
upper side
smooth
simple leaf
blade of one part
compound leaf
blade of several parts
leaflets
attached by petiolule
to an extension of the rachis
leaf structure
sessile leaf
or small
long and narrow
no petiole
self-shading
petiolate leaf
no shading
petiole
stalk
long, thin
Internal structure
epidermis
transpiration
water loss through epidermis
problem when soil is dry
hairy
must be reasonably waterproof
Mesophyll
inferior to the epidermis
palisade parenchyma
layer of cells
along upper surface
spongy mesophyll
open, loose aerenchyma
permits CO2 diffuse away
from stomata
Vascular Tissues
between palisade parenchyma & spongy mesophyll
midrib
also called midvein
lateral veins emerge
branch into minor veins
bundle sheath
fibers arranged in a sheath
bundle sheath extension
Petiole
transition of stem and lamina
leaf traces
stipules
2 small flaps of tisue
Initiation & Development of Leaves
Basal Angiosperms and Eudicots
Leaf primordium
base of angiosperm
extends as a narrow cone
grows taller than apical meristem
increases in thickness
cells are meristematic
Monocots
like eudicots
initiated by apical meristem cells
modifications
more water less phtosynthesis
less water more photosynthesis
depends on location
