Chapter 31, pages 668-691
Plant Anatomy-1 27:41-31:27
Plant Anatomy-3 19:43-30:30
I. Leaf Morphology
A. Function
B. Adaptation for function
1. Thin
2. Flat
3. Strengthened by veins
4. Veins for conduction
C. Morphology
1. Parts of the leaf
a. Petiole
c. Stipules
2. Lamina
a. Flat and expanded portion of the leaf
b. Netted veins
(1) Occurs only in dicots
(2) Can be pinnately netted
(3) Can be palmately netted
(1) Occurs only in monocots
(2) Veins run parallel from the base to the apex of the leaf
3. Petiole
a. Stalk on which the lamina stands
b. Stipules attached along the base of the petiole and are leaf-like in structure
c. Peltate - petiole attachment to center of lamina instead of base
d. Sessile - leaves with the petiole missing
4. Leaf arrangement
a. Simple - types of leaves described above (one "leaflet" per leaf)
b. Compound - two or more leaflets per leaf
(a) Leaf in same form as a bird feather
(b) Main axis is called a rachis
(a) Several leaflets attached to the petiole at the same point
(b) Same form as the palm and fingers of your hand
c. Three criteria for distinguishing between simple and compound leaves
(1)
Buds
occur in
axils
of leaves only, not in axils of leaflets, thus, if the
"leaves" contain no buds in their axils
then the "leaves" are really leaflets of a
compound leaf.
(2) Each leaf on a branch stands oriented in a different
plane while the
leaflets of a compound leaf all stand
oriented in the same plane. Thus, if all
the "leaves" of a "branch" are in the
same plane, then the "branch" is really a
compound leaf.
(3) In deciduous trees and shrubs, leaf always falls naturally
in tact. Thus,
if there is a question if a leaf is compound,
if the leaves on the ground are a
cluster of leaflets, then the leaf is
compound.
D. Four types of leaves:
1. Dicot leaves - dicot leaves are net-veined
2. Monocot leaves - monocot leaves are parallel-veined
3. Grass leaves
a. Blade - the flattened lamina portion
b.
Sheath
- the lower end of the flattened portion that surrounds the stem and
attaches to the
node
below
c.
Ligule
- a small flap of flat tissue extending up from the
sheath
(parallel to the
sheath) at the union of the sheath and
blade
(perpendicular to the
blade)
d.
Auricles
- small fingers of tissue extending around the stem (parallel to the
blade and perpendicular to the sheath) at the union of the sheath
and the blade
4. Gymnosperm leaves
a.
Needle-like
leaves - leaves long and slender like a needle,
pines
and
firs
are
a good example
b.
Scale-like
leaves - leaves are very small and usually green,
cedars
and
junipers
are good examples
c. Fan-shaped leaves - leaves are broad like an
oak
leaf but more in the shape
of a
fan,
ginkgos
are the only example of this type of
gymnosperm
leaf
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