leaves botany Flashcards
Leaves are flat
and thin for
maximum
absorption of
light and gas
All leaves originate
as
primordia
support
leaves to have and
ideal cylindrical
structure of foliage.
Stems
large, flat,
green structure that
photosynthesizes
Leaf:
Blade is
divided into
leaflets
COMPOUND
With a single
blade
SIMPLE
Leaflets in pairs along rachis (petiole)
Pinnately compound
leaflets are further subdivided
Bipinnately compound
All leaflets are attached at same point at the end of petiole
Palmately compound
Play major role in movement of water absorbed by roots
leaves
occurs when water evaporates from leaf surface.
Transpiration
Root pressure forces water out hydathodes at tips of
leaf veins in some plants.
Guttation -
attachment of leaves to stems
Nodes
stem regions between two nodes.
Internodes
Arrangement of leaves on stem
alternate, opposite, whorled
one leaf per node
Alternate
two leaves per node
Opposite
three or more leaves per node
Whorled
Main midvein included within enlarged midrib.
Secondary veins branch from midvein.
Pinnately veined leaves
Several primary veins fan out from base of blade.
Palmately veined leaves
Monocots
Primary veins are parallel
Parallel venation
Dicots
Primary veins divergent in various ways
Netted / Reticulated venation
Veins fork evenly and progressively from base of blade
Dichotomous venation
Single layer of cells covering the entire surface of the leaf
Devoid of chloroplasts
Coated with cuticle (with cutin)
Functions to protect tissues inside leaves
Epidermis
Lower epidermis typically has thinner layer of ______and is
perforated by numerous _____
cutin and stomata.
bordered by two guard cells.
Stomata
originate from the same parent cell, and contain chloroplasts.
guard cells
Regulate gas exchange between leaf interior and atmosphere
Regulate evaporation of water
stomata
Regulate gas exchange between leaf interior and atmosphere
Regulate evaporation of water
stomata
Most photosynthesis takes place in the
mesophyll
Compactly stacked, barrel-shaped parenchyma cells, commonly
in two rows
Contains most of leaf’s chloroplasts
Palisade mesophyll
Loosely arranged parenchyma cells with abundant air spaces
Spongy mesophyll
partly collapse under dry conditions.
Causes leaf to fold or roll, reducing transpiration
Bulliform cells
Consist of xylem and phloem tissues surrounded by
bundle sheath of thicker-walled parenchyma
Veins (vascular bundles)
have limited availability of water, wide
temperature ranges, and high light intensities.
Arid regions
Less xylem and phloem
Mesophyll not differentiated into palisade and spongy
layers.
Large air spaces
Leaves of Aquatic Areas
Modified leaves that curl
around more rigid objects,
helping the plant to climb
or to support weak stems
Tendrils
Modified leaves that reduce leaf
surface and water loss and
protect from herbivory.
Spines
Leaf tissue replaced with
sclerenchyma.
Photosynthesis occurs in stems
Cacti
Modified stems arising in the
axils of leaves of woody
plants
Thorns
Outgrowths from epidermis
or cortex
Prickles
are
modified for water storage.
Have parenchyma cells with
large vacuoles
Many desert plants
Succulent leaves
store
carbohydrates.
Onions, lily
Fleshy leaves
Leaves develop into urn-like
pouches that become home of ant
colonies.
Flower-pot leaves
Leaves buried in ground, except
for exposed end.
Window leaves
- New
plants at leaf tips
Walking fern
Tiny plantlets
along leaf margins
Air plant
At bases of flowers or flower stalks
Floral Leaves
Flowers do not have petals, instead
brightly colored bracts surround flowers.
Clary’s sage - Colorful bracts are at top of flowering
stalks above flowers.
Poinsettia -
Grow in swampy areas and bogs
Nitrogen and other elements are deficient in soil.
Specialized leaves trap and digest insects.
Insect-trapping leaves
Insects trapped
and digested
inside
cone-shaped
leaves.
Pitcher Plant
Have round to oval
leaves covered with
glandular hairs that have
a sticky fluid of
digestive enzymes at tip
Sundews
Only in North
Carolina and
South Carolina
Blade halves trap
insects.
Venus Flytrap
Submerged or
floating in shallow
water
Tiny bladders on
leaves have trap
doors that trap
insects inside
bladders.
Bladderwort
may also be present in the vacuole.
Water soluble anthocyanins (red or blue) and
betacyanins
drop leaves seasonally.
Deciduous plants
Cells coated and impregnated
with suberin.
Protective layer
Pectins in middle lamella of
cells are broken down by
enzymes.
Separation layer
