Leaves

Leaves

Organ that forms the main lateral appendage on the stem of vascular stem

Green structures involved in photosynthesis

Leaf primordium

• extends upward than shoot apical meristem

• Consists of protoderm, ground meristem, provascular tissues (forms 1 ̊ xylem/ phloem)

lamina

young immature leaf

Photosynthesis

Chlorenchyma, flat thin leaf

Transpiration

• the process by which plant loses water to serve the following purposes:

  • Continuous uptake of water

  • Cooling effects

  • Controls degree of saturation of cell with water

Aloe

used as Mild Topical Anesthetic

Ginkgo

used as Anticoagulant

Duhat

used as Antibacterial

Marigold

used as Antifungal

Lamina/leaf blade

flat, light harvesting portion

Apex

tip of the leaf

Margin

outline of the leaf

Veins

 vascular tissue of the leaf

midrib

most prominent vein

Base

where petiole attaches to

Petiole

Stalk that attaches the leaf to the stem, holds blade

Petiolate

has a petiole

Sessile

has no petiole

Stipule

Added photosynthesis, for protection

1. a small leaflike appendage to a leaf, typically borne in pairs at the base of the leaf stalk.

Simple

with one blade only

Compound

with a blade divided into leaflets or pinnae or pinnule

Palmately compound

• Leaflets attach to same point

• Leaflets are attached to the end of the petiole

Bifoliate

having only two leaves

Trifoliate

having only three leaves

Quadri/tetrafoliate

having only four leaves

Pentafoliate

having only five or more leaves

Pinnately compound

Leaflets attach indvl to rachis by petiolule

Simple Pinnately Compound

possess primary rachis

Bipinnately Compound

possess primary and secondary rachis

Tripinnately Compound

Possess primary, secondary, & tertiary rachis

Veins

• bundles of vascular; distribute water from stem into leaf and collect sugars produced and carry them to the stem for use or storage

Venation pattern

Arrangement of veins on the blade

Parallel

• a vein configuration in which the veins run parallel to one another

Netted

the leaf veins form a lace-like skeleton of veins

Pinnately netted

Veins arise from the midrib

Radiately netted

Principal veins arise from the center of the blade

Palmately netted

Principal veins arise from the base of the blade

Leaf traces

vascular bundles w/c exit the stem and diverge to the petiole

Phyllotaxy

• Arrangement of leaves on the stem

• Ex. Alternate, Opposite, Spiral, Decussate (right angle), Whorled

Leaf margin

Ex. undulate, entire, serrate, lobed

Guard cells

kidney-shaped, chlorophyllous epidermal cells

Leaf Traces

Vascular bundle which exit the stem and diverge to the petiole

Epidermis

• With cutin

• Flat epidermal cells, with guard cells, trichomes

• High # stomata in lower epidermis

Trichomes

• prevents rapid air movt, prevents water loss fr stomata; protection

Stomatal crypts

filled w/ trichomes & stomata, at lower surface of leaf, decrease air movt near stomata

Mesophyll

Ground tissue

Palisade parenchyma

• Uppermost, main photosynthetic tissue

• 1 layer thick, cells are separated, inc exposure to

• CO₂

• Larger and enlongated

Spongy mesophyll

• Open , loose aerenchyma, permits CO2 to diffuse rapidly fr stomata into all parts of leaf

• Smaller and spirical

Vascular tissues

• Found in the vein (vasculat bundle)

• Between palisade , spongy mesophyll

Minor veins

important in releasing water from xylem and loading sugar into phloem

Bundle sheath

fibers arrange as sheath around vascular tissue, present in midrib and lateral veins only

Bulliform cells

• Large vacuolated epidermal cells that inroll the leaf during hot conditions.

• Present only in monocot epidermal cells

• Rolling or curling of leaves to preserve water

Kranz anatomy

• Typical of monocot leaf that undergoes C4 metabolism, plants possess mechanism of CO₂ transport, adapt C4 plants in dry environment

• These plants lack palisade and spongy mesophyll layer but with prominent bundle sheath with large chlorophyllous cells

PINE NEEDLE LEAF

Vascular bundle produce new phloem each year but no new xylem

Abscission Zone

• Detachment are of leaves from the stem

• Release enzymes which weaken their walls

Senescence

Leaf aging due to breakdown of chlorophyll, sugars and loss of photosynthetic ability

Leaf scar

Protective scar tissue across wound after leaf fall

Succulent Leaves

• Thick and fleshy (parenchyma stores water), reduced surface

Senecio

Spherical succulent leaves

Dinteranthus

Pair of succulent leaves

Lithops

• pair of translucent leaves acting as optical fiber, allows light to enter, even leaves are under ground

Spines

• no blade and needle-shaped, no mesophyll, no vascular tissue, has closely packed fibers in mesophyll

Tendrils

• Sensing contact with other objects, no lamina, support; side facing the object stop growing, otherside elongate – coil

• Ex. Pea plant, Squash plant

Insect traps

digest insects and obtain nitrogen for their amino acid

Ex. Nepenthes (pitcher plant), Sundew (with stalked glands),

Passive trap

• incapable of mov

• ex. Pitcher plant

Active trap

• leaf blade curl, close

• Ex. Venus’ flytrap (traps insect)

Adventitious buds

• produce plantlets at the margin

Kalanchoe

With plantlets along the leaf margin

Sansiviera

Reproduce by leaf cutting

Colored leaves

• for attraction

• Ex. Poinsettia, Bougainvillea, Anthurium (colored spathe)

Floats

• aerenchymatous leaf base for buoyancy, support

• Ex. Water hyacinth

Pseudotrunk

Supporting leaf bases

for support

Motile leaves

• display “thigmonasty” sensitivity to touch

• for protection

Thigmotropic response

tropic response to touch

Stipule

Expanded leaf-like petiole

• Added photosynthesis

• Ex. Suha leaf, Rose leaf