Leaves
External Structure of Foliage Le 
aves
leaves absorb carbon dioxide
using light energy
convert into charbohydrate
Initiation and Development of Leaves
light-harvesting portion
leaf blade
called lamina #
blade's lower side
dorsal surface
blade's upper side
ventral surface #
adaxial (usually) smooth)
leaves have petiole
long
thin
flexible petioles
flutter in wind
cooling the leaf
bringing fresh air to its surface #
Internal Structure of Foliage Leaves
Epidermis
Thin foliage leaves #
produce through
Shoot apical meristem
forming a
protrusion
a leaf primordium
the primordium #
leaf protoderm
leaf
ground meristem
cells are meristematic
strand of cells
provascular tissue
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primary xylem and phloem
young bundle in stem
Development state
Dormant
Parts of resting terminal
Auxiliary bud
cell division may occurs
only maturation
especially the synthesis of
chlorophyll
cutin
Wax
Seed acting like perennial plants
Initial leaves
before seed
Dormant
become
Dry
Inside a developing fruits
Absorb water #
expand rapidly #
During germination
Monocot
eudicots
are initiated
by the expansion of some shoot
apical meristem cells to form a leaf primordium
gives rise to the lamina
some monocot
becomes broad and expanded like a eudicot
lamina, but grasses, lilies, and many others have linear, strap-shaped leaves that
grow continuously,
Alternate
Photosynthesis Without Leaves
may occur in tissues other than foliage leaf mesophyll
stem cortex
bark
Morphology and Anatomy of Other Leaf Types
Succulent Leaves
Sclerophyllous Foliage Leaves
Leaves of Conifers
Bud Scales
Spines
Leaves with Kranz Anatomy
Tendrils
Insect Traps
The ability to trap
and digest insects has evolved in several families.
leaves lack palisade parenchyma
spongy
mesophyll
special metabolism
called C4 photosynthesis
bud scale structure differs from that of
foliage leaves
tendrils grow indefinitely
contain cells that are capable of sensing contact with an object
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The soft, flexible
blade of a photosynthetic leaf is useless as a protective device against herbivores,
but spines have no blade and are needle shaped; mutations that inhibit lamina
formation have been selectively advantageous
they have a thick cuticle,
and their epidermis and hypodermis cells have thick walls
leaves are sclerophylls #
primarily protection,
no photosynthesis
Inside the leaf, the mesophyll contains very few air spaces,
A lack of air
spaces also makes the mesophyll more transparent, just as pure water is more
transparent than soap bubbles or foam, allowing light to penetrate farther into the
leaf
Used photosynthesis
Foliage leaves must produce more sugars by photosynthesis than are used in their
own construction and metabolism, or the plant would lose energy every time it
produced a leaf. This limits the amount of sclerenchyma in foliage leaves, and most
leaves therefore tend to be soft, flexible, and edible.
Mesophyll
Vasular Tissue
Petiole
Flat in shape
The epidermis must be reasonably waterproof but simultaneously
translucent, and it must allow entry of carbon dioxide. Leaf and stem epidermises
are basically similar, consisting of a large percentage of flat, tabular
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Palisade cells are separated slightly so that each
cell has most of its surface exposed to the intercellular spaces. Because carbon
dioxide dissolves into cytoplasm slowly, the large surface gives maximum area for
dissolution; tightly packed cells could not absorb enough carbon dioxide for
efficient photosynthesis
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Veins, especially larger ones, often have a mass of fibers above, below, or both—
the bundle sheath extension (Figure 6-26). Such fibers help give rigidity to the
blade and are believed to provide an additional means by which water moves from
the bundle out to the mesophyll
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Petioles may be tiny but are massive in plants like palms, rhubarb, celery, and water
lilies. They are considered to be part of the leaf and are the transition between the
stem and the lamina