External and Internal Structure of Leaves Flashcards
§ An organ of a vascular plant;
lateral outgrowth of the stem
§ It is usually green, flat lateral
structure that protrudes from a
plant’s stem to collect sunlight for
photosynthesis, and the site
where transpiration takes place
leaf
FUNCTION OF LEAVES
§ The process of producing food, that occurs
mainly in the leaves of most angiosperms.
§ This process essentially involves the
absorption of light mainly by the chlorophyll
pigments and the absorption of carbon
dioxide via the stomatal pores in the leaves.
§ As a result of the cleavage of water
molecule during photosynthesis, oxygen is
generated and released to the atmosphere
Photosynthesis
FUNCTION OF LEAVES
§ Plants lose a large volume of water through
the leaves in the form of vapor.
§ The exit of water is through the stomata and
the cuticle, but stomatal transpiration is largely
more dominant than cuticular transpiration.
§ It is estimated that the loss of water via
stomata through the process of transpiration
exceeds 90% of the water absorbed by the
roots
Transpiration
FUNCTION OF LEAVES
§ the plant leaves synthesize and
translocate the flower-inducing
hormone called florin to the buds
Floral Induction
FUNCTION OF LEAVES
Food Storage
Special Uses
a broad, flat part of the leaf
blade, lamina
a stemlike part of the leaf that joins the blade to the stem
petiole
two small flaps that grow at the base of the petiole of some
plants
stipules
a strong, thick vein that
runs through the leaf blade from its
base to its apex; continuation of the
petiole and serves for conduction
midrib
thinner, lateral branches of
the midrib; for conduction
veins
tiny openings or pores in
plant tissue that allow or gas
exchange
stomata
these are two
sausage or dumbbell-shaped cells
that surround the stomata and
function to open and close stomatal
pores
guard cells
it is where
photosynthesis takes place
mesophyll
the
uppermost mesophyll that
consists of compactly stacked,
barrel-shaped parenchyma cells
that are in two rows; contains
more than 80% of the leaf’s
chloroplast
palisade mesophyll
lower region;
consists of loosely arranged
parenchyma cells with abundant air
spaces between them; its cells also
have numerous chloroplast
spongy mesophyll
scattered throughout the
mesophyll; consist of xylem
and phloem tissues
surrounded by a jacket of
thicker-walled parenchyma
cells called the bundle
sheath; gives the leaf its
“skeleton”
veins/vascular bundles
SPECIALIZED LEAVES
VEGETATIVE REPRODUCTION
AERATION
SUPPORT
PROTECTION
STORAGE
ATTRACTION
ABSORPTION/DIGESTION
with platelets or buds that
may grow along the notches,
bases, apices and tips of
blades and petioles.
Ex: Kataka-taka
Vegetative Reproduction
with enlarged
petiole for buoyancy.
Ex: Water hyacinth
aeration
presence of tendrils, hooks
and supporting leaf bases.
Ex: squash tendrils
support
presence of bud scales,
motile leaves, spines, stipules and
bracts.
Ex: cactus, pineapples
protection
with succulent leaves that
retain water in their large, thin walled
parenchyma cells.
§ Ex: cactus, aloe vera, bulb of onion
storage
with petaloid flower bracts
or brightly variegated leaves of some
plants
Ex: poinsettia, bougainvillea, anthurium
attraction
