Angiosperms V
Primary Growth:
Leaves
Leaf Morphology
Leaves are arranged
on stems in either an
opposite, alternate, or
whorled pattern
 This arrangement is
called the phyllotaxis
 Most leaves are either
simple or compound

A SIMPLE LEAF
External Leaf Morphology


The leaf blade is
connected to the
stem by the petiole
Other leaf parts
include: base,
margin, apex,
venation
base
petiole
venation
margin
apex
Simple Leaves
Compound
Leaves

Pinnately compound
leaves are similar to
ferns: leaflets
attached along a
rachis

Palmate leaves have
leaflets attached at
one point
Simple vs. Compound Leaves
Axillary buds occur at the base of
each leaf - not at the base of leaflets
 The abscission layer forms at the
base of the leaf’s petiole - not at the
base of a leaflet
 Leaflets are generally all produced
in the same plane - leaves have a
phyllotaxis

Internal
Structure
(eudicot)
Internal Structure (monocot)





Upper
epidermis
Bulliform
cells
Mesophyll
Veins with
bundle
sheath cells
Guard cells
Action of Bulliform Cells (open)
Action of
Bulliform
Cells (closed)
Leaf Abscission



Abscission takes place
at the base of the leaf
(not leaflets)
Response to
hormones triggered
by environment
changes
Two regions:
–
–
Separation layer
Protective layer
Variations and Uses






Multiple epidermal layers
Thick cuticles
Many trichomes (African
violet)
Stomata in sunken pits with
trichomes (xerophytes)
Stomata only on the upper
surface (water lilies)
Leaves modified to be tendrils
or spines
Variations and Uses (cont.)

Carnivorous plants
(specialized for
obtaining mineral
nutrients in wet or
mineral poor
habitats)
–
–
–
Venus fly trap
Sundew
Pitcher plants
Sundew
Pitcher Plants
Variations and
Uses (cont.)

Leaves for
human
consumption or
use as
medicines, dyes,
fibers, waxes
and for
smoking