LEAVESLEAVES(daun)(daun)

The primary functions of The primary functions of leaves:leaves:

PhotosyntesisPhotosyntesis TranspirationTranspiration

Leaf Function:Leaf Function:

Leaves are the powerhouse of plants. In Leaves are the powerhouse of plants. In most plants, leaves are the major site of food most plants, leaves are the major site of food production for the plant. Structures within a production for the plant. Structures within a leaf convert the energy in sunlight into leaf convert the energy in sunlight into chemical energy that the plant can use as chemical energy that the plant can use as food. Chlorophyll is the molecule in leaves food. Chlorophyll is the molecule in leaves that uses the energy in sunlight to turn water that uses the energy in sunlight to turn water (H(H22O) and carbon dioxide gas (COO) and carbon dioxide gas (CO22) into ) into sugar and oxygen gas (Osugar and oxygen gas (O22). This process is ). This process is called photosynthesis. called photosynthesis.

Leaf Structure:Leaf Structure:

A leaf is made of many layers that are A leaf is made of many layers that are sandwiched between two layers of tough skin sandwiched between two layers of tough skin cells (called the epidermis). The epidermis also cells (called the epidermis). The epidermis also secretes a waxy substance called the cuticle. secretes a waxy substance called the cuticle. These layers protect the leaf from insects, These layers protect the leaf from insects, bacteria, and other pests. Among the bacteria, and other pests. Among the epidermal cells are pairs of sausage-shaped epidermal cells are pairs of sausage-shaped guard cells. Each pair of guard cells forms a guard cells. Each pair of guard cells forms a pore (called stoma; the plural is stomata). pore (called stoma; the plural is stomata). Gases enter and exit the leaf through the Gases enter and exit the leaf through the stomata. stomata.

Dicotyledonous leavesDicotyledonous leaves

Is composed of two principal parts:Is composed of two principal parts: Blade or laminaBlade or lamina Petiole or stalkPetiole or stalk Netted venationNetted venation

Monocotyledonous Monocotyledonous leaves:leaves:

Is divided into two parts:Is divided into two parts: SheathSheath BladeBlade Paralled venationParalled venation

There are two kind of There are two kind of leaves:leaves:

Types of LeavesTypes of Leaves

Simple: not divided into leaflets; leaf composed of one blade

Compound: consists of two or more leaflets

Pinnately Compound: feather-like; leaflets along each side of a common axis.

Bipinnately Compound: primary and secondary divisions are pinnate.

Palmately Compound: 3 or more leaflets radiating from a common point.

Trifoliate: three leaflets

Single Needle

Scale-like

Awl-shaped

Cordate: heart-shaped.

Alternate: leaves are arranged singly at different heights and on different sides of the stem.

Opposite: leaves are directly across from each other on the stem.

Elliptic: broadest in the middle and narrower at each end.

Flabellate: fan-like.

Lanceolate: longer than wide, broadest below the middle and tapering to the apex.

Obovate: inversely ovate, broadest above the middle

Ovate: egg-shaped, broadest below the middle

Broad Ovate: wide, egg-shaped

Leaf Margins

Leaf Margins:

Leaves come in many sizes and shapes; they are often used to help identify plants. Some leaves are flat and wide; others are spiky and thin. Plant spines (like cactus spines) are actually modified leaves.

Plant Parts – LeafPlant Parts – Leaf

ArrangementArrangement ShapesShapes ColorColor Vein PatternVein Pattern Form – Simple or CompoundForm – Simple or Compound MarginMargin SurfaceSurface

Leaf Arrangement – Leaf Arrangement – SimpleSimple

Leaf Arrangement – Leaf Arrangement – CompoundCompound

Leaf ShapeLeaf Shape

Vein Vein PatternPattern

PinnatePinnate PalmatePalmate ParallelParallel DichotomousDichotomous

Leaf MarginLeaf Margin

Leaf SurfaceLeaf Surface

GlabrousGlabrous PubescentPubescent VillousVillous TomentoseTomentose

ScabrousScabrous GlaucousGlaucous RugoseRugose GlandularGlandular

•There are 8 common leaf surfaces.

Leaf Surface – GlabrousLeaf Surface – Glabrous

The surface is smooth, not hairy.The surface is smooth, not hairy.

Leaf Surface – PubescentLeaf Surface – Pubescent

Short, soft hairs cover the surface.Short, soft hairs cover the surface.

Leaf Surface – TomentoseLeaf Surface – Tomentose

Covered with wool-like hair.Covered with wool-like hair.

Leaf Surface – ScabrousLeaf Surface – Scabrous

Covered with short, prickly hairs.Covered with short, prickly hairs.

Leaf Surface – GlaucousLeaf Surface – Glaucous

Covered with a bluish-white waxy Covered with a bluish-white waxy substance.substance.

Leaf Surface – RugoseLeaf Surface – Rugose

Surface is wrinkly.Surface is wrinkly.

Leaf Surface – GlandularLeaf Surface – Glandular

Glands filled with oil or resin cover the Glands filled with oil or resin cover the surface.surface.

Anatomy of the foliage leaf:Anatomy of the foliage leaf:

In the leaves of most trees, three distinct tissue layers In the leaves of most trees, three distinct tissue layers can be discerned in their leaves. These are:can be discerned in their leaves. These are:

1.1. The epidermisThe epidermis with its cuticle and stomata with its cuticle and stomata 2.2. TheThe mesophyllmesophyll where most of the where most of the chloroplasts are found and photosynthesis takes placechloroplasts are found and photosynthesis takes place 3. 3. The leaf veinsThe leaf veins which transport water and inorganic which transport water and inorganic compounds into the leaf, and organic compounds compounds into the leaf, and organic compounds produced by photosynthesis away from the leaf, to produced by photosynthesis away from the leaf, to other parts of the plant. other parts of the plant.

Cross section of a leaf, showing the anatomical features Cross section of a leaf, showing the anatomical features important to the study of photosynthesis: stoma, guard cell, important to the study of photosynthesis: stoma, guard cell,

mesophyll cells, and veinmesophyll cells, and vein

EpidermisEpidermis The The epidermal tissue functions in prevention of water functions in prevention of water

loss and acts as a barrier to fungi and other invaders. loss and acts as a barrier to fungi and other invaders. Thus, epidermal cells are closely packed, with little Thus, epidermal cells are closely packed, with little intercellular space. To further cut down on water loss, intercellular space. To further cut down on water loss, many plants have a waxy many plants have a waxy cuticle layer deposited on top layer deposited on top of the epidermal cells. of the epidermal cells.

Guard CellsGuard Cells To facilitate gas exchange between the inner parts of To facilitate gas exchange between the inner parts of

leaves, stems, and fruits, plants have a series of leaves, stems, and fruits, plants have a series of openings known as openings known as stomata (singular stoma). They (singular stoma). They regulate exchange of water vapor, oxygen and carbon regulate exchange of water vapor, oxygen and carbon dioxide through the stoma. dioxide through the stoma.

Collenchyma cells support the plant. These cells support the plant. These cells are charcterized by thickenings of the cells are charcterized by thickenings of the wall, they are alive at maturity. They tend to wall, they are alive at maturity. They tend to occur as part of vascular bundles or on the occur as part of vascular bundles or on the corners of angular stems. corners of angular stems.

Sclerenchyma cells support the plant. They cells support the plant. They often occur as bundle cap fibers. often occur as bundle cap fibers. Sclerenchyma cells are characterized by Sclerenchyma cells are characterized by thickenings in their secondary walls. They are thickenings in their secondary walls. They are dead at maturity. A common type of dead at maturity. A common type of schlerenchyma cell is the fiber. schlerenchyma cell is the fiber.

Xylem Xylem Xylem is a term applied to woody ( is a term applied to woody (lignin--

impregnated)walls of certain cells of plants. Xylem impregnated)walls of certain cells of plants. Xylem cells tend to conduct water and minerals from roots cells tend to conduct water and minerals from roots to leaves. While parenchyma cells do occur within to leaves. While parenchyma cells do occur within what is commonly termed the "xylem" the more what is commonly termed the "xylem" the more identifiable cells, identifiable cells, tracheids and and vessel elements, , tend to stain red with Safranin-O. Tracheids are the tend to stain red with Safranin-O. Tracheids are the more primitive of the two cell types, occurring in the more primitive of the two cell types, occurring in the earliest vascular plants. Tracheids are long and earliest vascular plants. Tracheids are long and tapered, with angled end-plates that connect cell to tapered, with angled end-plates that connect cell to cell. Vessel elements are shorter, much wider, and cell. Vessel elements are shorter, much wider, and lack end plates. They occur only in lack end plates. They occur only in angiosperms, , the most recently evolved large group of plantsthe most recently evolved large group of plants

Phloem cells conduct food from leaves to rest of the plant. They are alive at maturity and tend to stain green (with the stain fast green). Phloem cells are usually located outside the xylem. The two most common cells in the phloem are the companion cells and sieve cells. Companion cells retain their nucleus and control the adjacent sieve cells. Dissolved food, as sucrose, flows through the sieve cells.

A Part of The LeafA Part of The Leaf11. Plastids:. Plastids: A green leaf is green because of A green leaf is green because of

the presence of a group of pigments the presence of a group of pigments known as chlorophylls. Minute structures known as chlorophylls. Minute structures called plastids contain the chlorophyll called plastids contain the chlorophyll within the leaf. within the leaf.

2. Carotenoid pigments2. Carotenoid pigments (yellow and (yellow and orange) are also found in plastids. The orange) are also found in plastids. The carotenoids occure, along with the carotenoids occure, along with the chlorophyll pigments, in tiny structures - chlorophyll pigments, in tiny structures - called plastids - within the cells of leaves. called plastids - within the cells of leaves. Sometimes they are in such abundance Sometimes they are in such abundance iin the leaf that they give a plant a yellow-iin the leaf that they give a plant a yellow-green color, Carotenoids are in many green color, Carotenoids are in many living things, giving living things, giving

3. Anthocyanin pigments3. Anthocyanin pigments (reds and (reds and purples) occur in the sap of cells. The purples) occur in the sap of cells. The anthocyanins temporarily color the edges anthocyanins temporarily color the edges of some of the very young leaves as they of some of the very young leaves as they unfold from the buds in early spring. They unfold from the buds in early spring. They also give the familiar color to such also give the familiar color to such common fruits as cranberries, red apples, common fruits as cranberries, red apples, blueberries, cherries, strawberries, and blueberries, cherries, strawberries, and plums. plums.

Basic leaf typesBasic leaf types

needle-shaped

•Ferns have fronds. •Conifer leaves are typically needle-, awl-, or scale-shaped •Angiosperm (flowering plant) leaves: the standard form includes stipules, a petiole, and a lamina. •Lycophytes have microphyll leaves. •Sheath leaves (type found in most grasses). •Other specialized leaves (such as those of Nepenthes)

Scale-shaped leaves

stellate trichomes

trichomes on the lower surface of a Coleus

•Opening and closing of the stomata by the paired guard cells controls the gas exchange rate. In some cases, the guard cells are supported by the subsidiary cells. •Guard cells act as ports between the environment and the interior of the leaf. When the guard cells accumulate water they become turgescent and open. Opening and closing in turn is controlled by light conditions, air humidity, temperature and the CO2 concentration. •Guard cells, in contrast to other epidermis cells, do possess chloroplasts.

Stomata open when the internal pressure of the guard cells rises as a result of water absorption. The pressure increases from 1.5 to 3.0 mega Pascal.

Since the walls of the guard cells are relatively flexible at the side of the stoma, the guard cells expand vertically and the stoma subsequentely opens.

Structure of a chloroplastStructure of a chloroplast

Pea Leaf Stoma, Vicea sp.

Tip of the leafTip of the leaf

Leaf AbscissionLeaf Abscission

The formation of a definite abscission zone The formation of a definite abscission zone across a petiole or fruit stem is responsible for across a petiole or fruit stem is responsible for leaf fall or fruit dropleaf fall or fruit drop

The function of the abcission zone :The function of the abcission zone : - to bring about the fall of the leaf or other plant - to bring about the fall of the leaf or other plant partpart - to protect the region of the stem from which - to protect the region of the stem from which the leaf has fallen against insect damage or the leaf has fallen against insect damage or rot caused by bacteria or fungirot caused by bacteria or fungi