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LEAVES 6a00e553466c0488340153902fd188970b-800wi (:forbidden: Morphology…
LEAVES
Concepts
leaves absorb carbondioxide and convert it in CO2 by using light energy.
Foliage leaves are most familiar leaves
External structure of Foilage leaves
most common function of foilage leaves is photosynthesis.
maintain amount of water.
flat harvesting part is the
leaf blade
.
the leaf blades lower side is its
dorsal surface.
Larger veins protrude like backbone
axial side.
the upper side is the
ventral surface face
and is smooth in nature.
most leaves have
petiole
.
:<3:Petiole
if the leaves donot have petiole is known as
sessile leaf
instead of
petiolate
.
leaf base wrap around the stem to form
sheathing leaf base.
leaf blade may be
simple or compound
.
simple lea
f has a blade just 1 part and
compound leaf
have blade divided into several individual parts.
Extension of petiole is called
rachis.
with in leaves are
veins
or bundle of vascular tissue.
Reticulate ventilation
occur in netted pattern in angiosperm and eudicots.
Parrallel ventilation
run side by side in monocots.
Abscision zone
presented at petiole.
Internal structure of Foilage leaves.
Epidermis
Water loss thriugh epidermis is called
trasnpiration.
should be waterproof and trasnculent.
Leaf epidermises are often hairy and trichomes affect the leaf biology.
Contains cutin and usually also a wax on their outer cells.
Ground tissues interior to the leaf
epidermis
re collectively called
Mesphyll
.
Lower surface pf leaf is
spongy mesophyll
Upper surface of most leaves is a layer of cells called
Palisade parenchyma or palisade mesophyll
.
Mesophyll
Vascular Tissue
:check: Between
Palisade and spongy mesophyll
are
vascular tissue.
:red_flag:from which
lateral vein
emerges and that branch into narrow
minor veins
.
:red_flag:
mid rib
called midvein.
:red_flag:
Bundle sheath
around vascular tissue.
:red_flag:
Bundle sheath extension
such fiber help give rigidity to to the blade.
Petiole
:<3:Petiole
Leaf Traces
branch from stem vascular bundle.
Stipules
protect the shoot apical meristem while the leaf is young and small.
Initiation and Development of leaves
Basal Angiosperms and Eudicots
Leaf primordium
that extends upward as a narrow cone.
Monocots
Monocot leaves like those of eudicots are nitated by the expansion of some shoot apical meristem.
in some monocots the lamia becoes broad and expanded like a eudicot lamina.
the laminas meristwmatic cells remain active mitotically.
the protoxylem and protopheom are constantly being steched and distrupted in the basal meristem.
Higher above the basal meristem tissues are mature, differentiation is similar to that for stems.
:forbidden: Morphology and anatomy of other leaf types.
:checkered_flag:Succulent Leaves
Succulent leaves are thick and fleshy.
Some leaves are cylindrical or even spherical.
Transparent allows to penetrate farther into the leaf.
Exposed leaf leaf tops allow sufficient light to enter and be conducted to the subterranean chlorenchyma.
:star:Sclerophyllous Foilage Leaves
Soft, Flexible and edible
Resistant to fungi, freezing tempetarure and ultravoilent light.
Present just below the epidermis and in the bundle sheaths.
:fire:Cuticle is very thick, and waxes are abundant on leaves of many sclerophyllous species.
:red_flag:Leaves of conifers
:pencil2: Coniferous leaves are screophylls have thick cuticle
epidermis and hypo dermis cells have thick walls.
Leaves are simple never compound.
lengths upto 12.5 cm and widths of 3.5 cm
Perennial reamaninig on the the stem for many years.
:no_entry: Bud scales
:check:primary function is protection, not photosynthesis.
:<3: Structure differs from foliage leaves.
:forbidden: Usually small and rarely compound, so wind damage is not a risk.
It frequently produce a thin layer pf corky bark
Provides greater protection than the simple epidermis of folage leaves.
:red_cross:
Spines
Distinct structure related to their function.
Have no blade and are needle shaped
:recycle:
Tendrils
:no_entry:Tendrils of many plants are from of modified leaves
It grows indefinitely and contain cells that are capable of sensing contact with a an object.
Coil around the object and use it for support.
:check:
Leaves with kranz anatomy
Special metabolism called C4 photosynthesis.
lack palisade and spongy mesophyll
transport carbondioxide
:!:
Insect trap
Ability to trap and digest insect
Contains numerous trichomes that secret a sticky digestive liquid.
Once insect is caught on a single trichome, adjacent trichomes are stimulated to bend toward the victim.
Short glands begin to secret digestive liquid.
After digestion and absorption are completed the midrib motor cells fill with water, swell and force the trap open ; ready for new victim
