Introduction of medicinal plants

Part (I) : The LeafPart (I) : The Leaf

II- ExamplesII- Examples

I- IntroductionI- Introduction

1 -Definition 4 -leaf structure

3 -Types of leaves 2 -Phyllotaxis

Introduction of Leaves

●Morphology

●Histology

●Definition

Leaves are lateral outgrowth from the stem with different function and structure.

Leaves are characterized by four main characters:

●They have a flattened form.

●Their texture is usually thin.

●Presence of chlorophyll.

●Presence of veins, which act as supporting and conducting strands.

1 -Definition 4 -leaf structure

3 -Types of leaves 2 -Phyllotaxis

Introduction of Leaves

●Morphology

●Histology

●Phyllotaxis:

1 -Alternative or spiral.

2 -Opposite.

3 -Opposite decussate.

4 -Whorled.

1 -Alternative or spiral 2 -Opposite

3 -Opposite decussate 4 -Whorled

Opposite

Opposite decussate

Whorled

Alternative or spiral

Q: Identify the following phyllotaxis?

1 -Definition 4 -leaf structure

3 -Types of leaves 2 -Phyllotaxis

Introduction of Leaves

●Morphology

●Histology

● Types of leaves:

1 -Cotyledons (seed-leaves):● Found on embryonic plants in the seed

● For storage of food

2 -Prophylls:

● First leaves borne on a branch

● Simpler in structure than ordinary leaves

3 -Foliage leaves:

● Ordinary green leaves

● Primary location of photosynthesis

4 -Bracts:

●Leaves having flowers or group of flowers in their axis

●Smaller than ordinary leaves

5 -Floral leaves:

●Like sepals, petals, stamens and carpels

●They have no buds in their axis

6 -Scale leaves:

●Found on all underground stem

●Enclose and protect rhizomes and buds

7 -Modified leaves:

●The whole leaf or part of leaf is modified in to special structure for special function.

●Tendril Climbing

Spines Protection

1 -Definition 4 -leaf structure

3 -Types of leaves 2 -Phyllotaxis

Introduction of Leaves

●Morphology

●Histology

● ●Leaf structureLeaf structure::

lamina

petiole

Base

1 -Base:

▪The base is slightly enlarged and attached to the stem at a node

▪In some cases, the leaf-base develops lateral outgrowths called stipules and the leaf is called stipulate leaf ( c.v : exstipulate leaf)

▪Both leaf-base and stipules serve for protection of axillary buds.

.

2 -Petiole:

▪ It is the small stalk developes between the leaf base and lamina .

▪ Vary in length or may be lacking entirely, in which case the leaf blade is described

as sessile.

▪ Absent sessile

present petiolate

3 -Blade:

▪ It is flattened terminal portion ▪ It is usually the largest part of a leaf.

Blade

●Morphology

● Histology

Morphology

Composition of lamina

Description )shape –size- apex – margin

-base- venation –surfacetexture(

Composition of laminaComposition of lamina

Lamina

SimpleLobed

)divided(Compound

11 - -Simple laminaSimple lamina

●The lamina consists of a continuous, undivided surface .

22 - -lobed laminalobed lamina

22 - -lobed laminalobed lamina

●When the lamina is cut up in to a number of lobes (incisions) connected together .

●If the incision is directed towards the midrib, the lamina is Pinnately-lobed.

●If the incision is directed towards the top of petiole, the lamina is called Palmately- lobed.

33 - -Compound laminaCompound lamina

●The lamina is completely segmented in to numbers of separate leaflets .

Compound

Binate Ternate Palmate Pinnate

Paripinnate Imparipinnate

Q: identify the following lettersQ: identify the following letters??

Morphology

Composition of lamina

Description )shape –size- apex – margin

-base- venation –surfacetexture(

Description of laminaDescription of lamina

1 -Shape 5- Base

2 -Size 6- Venation

3 -Apex 7- Surface

4 -Margin 8- Texture

1 -Shape: ●Oval ● Ovate ● Obovate

●Oblong ● Spathulate ● Cordate

●Lanculate ● Reniform ● Filliform

●Acicular ● Linear ● Tubular

●Ensiform

2 -Size :

The size doesn't exceed 30 cm long.

3 -Apex: ● Acute ● Acuminate

● Obtuse ● Mucronate

● Emarginate ● Recurved

4 -Margin: ● Entire ● Revolute

● Crenate ● Ciliate

● Serrate ● Dentate

5- Base: ●Symmetric ● Asymmetric

●Decurrent ● Cordate

●Reniform

6 -Venation: ● Parallel

● Reticulate

Pinnately-reticulate Palmately-reticulate

7 -Surface:

● Smooth ● Punctate

●Rugose ● Glabrous

●Pubescent

8 -Texture:

●Membraneous ● Papery

●Coriaceous ● Succulent

1 -Definition 4 -leaf structure

3 -Types of leaves 2 -Phyllotaxis

Introduction of Leaves

●Morphology

●Histology

Histology of laminaHistology of lamina

The Epidermis

Mesophyll

Histology of laminaHistology of lamina

11 - -EpidermisEpidermis ●Definition: The epidermis is the outer layer

of cells covering the leaf on the top and bottom .

●Function: For protection the other layers of leaf tissue & regulation of gas exchange.

●The epidermis is coated on the outer side with a waxy cuticle that prevents water

loss .

●The epidermis is covered with pores called stomata that regulate the exchange of gases and water vapor between the outside air and the interior of the leaf. Typically, the stomata are more numerous over the lower epidermis than the upper epidermis.

●Some leaves have hairs (pubescence), which are extensions of epidermal cells

) Trichomes.(

CuticleCuticle

●Definition: The cuticle is a protective layer covering epidermis of the green and aerial parts of plants.

●Function: It protects the plant against water loss, environmental stresses (support) as

well as microbial pathogens and insects .

●The amount of cutin on a leaf is affected by environmental conditions

1 -sunlight intensity 2 -wet or dry climate

●Epidermal cells usually do not exactly fit together, but there are small voids between the individual cells.  These voids between individual epidermal cells are filled up by cuticle plugs which are

termed anticlinal walls.  

Anticlinal wallAnticlinal wall

1 -Straight 2- Sinous 3- Wavy 4- Beaded

StomataStomata

●A stoma (pl. stomata) is a pore, found in the leaf and stem epidermis that is used for gas exchange.

●The pore is bordered by a pair of specialized parenchyma cells known as guard cells which regulate the size of the

opening .

Types of stomata

There are 4 basic types of stomata, these types are distinguished on the basis of the subsidiary cells surrounding the stomata & their arrangements.

A) Anomocytic typeB) Anisocytic typeC) Paracytic typeD) Diacytic type

A) Anomocytic type

The surrounding epidermal cells have no special arrangement,, so all the cells are normal epidermal cells without any modification.

B) Anisocytic type The stomata is surrounded by 3 or more subsidiary cells, one of them is distinctly

smaller than the others .

C) Paracytic typeC) Paracytic typeEach stoma is surrounded by 2 subsidiary Each stoma is surrounded by 2 subsidiary cells that have their long axis parallel to the cells that have their long axis parallel to the

axis of poreaxis of pore . .

D) Diacytic type

Each stoma is surrounded by 2 subsidiary cells having their long axis perpendicular to the pore.

Q: identify the following lettersQ: identify the following letters??

A B

C D

TrichomesTrichomes

●Definition: Hairs are a natural projections outside the epidermal tissues with various

shapes, size and characters .

●Function:1 -protection 2- secretory organ

3 -decrease rate of transpiration in desert plants .

Types of hairsTypes of hairs

Hairs

Non glandular hairs Glandular hairs

I- Non glandular hairsI- Non glandular hairs Non glandular hairs

Unicellular Multicellular

Branched Non branched Non branchedBranched

Simple

Stellate

Peltate

uniseriate

biseriate

pluriseriate

II- Glandular hairsII- Glandular hairs

Glandular hairs

Unicellular Multicellular

Branched Non branched

unicellular multicellular

Non branched stalk

Unicellular head

Bicellular head

Multiicellularhead

Uniseriate stalk with unicellular head

biseriate stalk with biseriate head

pluriseriate stalk with multicellular head

Description of epidermisDescription of epidermis 1 -Shape

)tubular–polygonal elongated–polygonal isodiametric(

2 -Anticlinal wall )straight – sinous – wavy –beaded(

3 -Cuticle )smooth – striated(

4 -Stomata)anomocytic – paracytic – diacytic - anisocytic(

5 -Hair types6 -Content

Q: Describe the following lettersQ: Describe the following letters??

A B

C D

Q: Describe the following lettersQ: Describe the following letters??

12 543 6

78

9

11

10

12

1314

15

22 - -MesophyllMesophyll

●Definition:

Tissue located between the upper and lower epidermis.

●Divided into:

a- Palisade mesophyll

b- Spongy mesophyll

Palisade mesophyll Spongy mesophyll

●Columnar

●Narrow intermolecular spaces

●Closely packed

●According to disposition of mesophyll

a- Isobilateral

b- Dorsiventral

●Irregular

●Wide intermolecular spaces

●loose

Contents as key elementsContents as key elements

Ca oxalate

crystals

Calcium oxalate crystalsCalcium oxalate crystals

Prisms Crystal sheath

Cluster Crystal layer

Raphides Idioblast