PLANT ANATOMY

The science of the structure of the organized plant body learned by dissection is called Plant Anatomy.In general, Plant Anatomy refers to study of internal morphology, pertaining to different tissues. the study of plant cell and tissue structureThe anatomy is one of branches of appearance Morphology where he teaches a plant form of the study of plant form apparent (abroad) is attributable to the taxonomy (Taxonomy= internal morphology)(Anatomy = internal morphology)

Plant tissues Systems

Like other organisms, plant cells are grouped together into various tissues. These tissues can be simple, consisting of a single cell type, or complex, consisting of more than one cell type.

Classification of tissues :Can be divided into plant tissue in the body based on the following : 1- Position2- Type of cells3- origin 4- Function

Tissue is a mass of similar or dissimilar cells performing a common function.

:Tissues of MeristemsMeristematic tissues are composed of cells that divide continuously

Function Meristems- Cell division- Cell elongation- Cell differentiation

Classification of meristemsApical meristems: located at the growing points of stems and roots e.g. those present in stem and root apices.Intercalary meristems: present between two permanent zone, present at base of internodes e.g. sugarcane and maize.Lateral meristems : present laterally and cause increase in diameter of plant. Located parallel to the longitudinal axis of the member plant

Classification of meristems

Lateral meristems

Intercalary meristems

Apical meristems

:Different types of mature tissuesa- Parenchyma b- Collenchyma c- Sclerenchyma d- Epidermish- Pericycle f- Endodermisj- Laticiferous tissue r- Cork (phellem) t- Tracheary tissue i- Sieve tissue s- Secretory structures n- Vascular tissue k –Nectaries

(Permanent Tissues (Mature Tissues

The permanent tissues are formed by the differentiated cells, which become specialised to perform specific functions like protection, support, storage and conduction. The permanent tissues always differentiate from the meristematic cells, during the process of growth.The three kinds of mature tissues are dermal, vascular, and ground tissues. Primary dermal tissues, called epidermis, make up the outer layer of all plant organs (e.g., stems, roots, leaves, flowers). They help deter excess water loss and invasion by insects and microorganisms.

Types of Permanent TissuesThe permanent tissues can broadly be distinguished into two types, namely

1 .Simple permanent tissue:Tissues which are composed of two or more types of cells but contribute to a common function are called complex tissues. Xylem and phloem are the complex permanent tissues. They together form the vascular bundle.This tissue consists of only one type of cells, e.g. parenchyma, collenchymas and sclerenchyma.

2 .Complex permanent tissue:This tissue is composed of more than one type of cells.Complex Tissue:

Tissues which are composed of two or more types of cells but contribute to a common function are called complex tissues. Xylem and phloem are the complex permanent tissues. They together form the vascular bundle.

Parenchyma:

Characters:1 -Simple living

cells.2 -Have primary

cellulosic thin wall with simple pits.

3 -Have intercellular spaces.

4 -They may be elongated, isodiametric or lobed.

Occurrence:

1 -In cortex and pith of stems and roots.

2 -Associated with xylem and phloem.

3 -In leaves and fruits.

Function:

1 -In aeration.2 -In photosynthesis.

3 -Storage of water, protein, minerals, etc..

4 -May become meristematic and divide .

2 -Collenchyma

Characters:1 -Simple living tissue.

2 -Have primary cellulosic thick wall with simple pits.

3 -May have intercellular spaces.4 -They are elongated cells.

Types:

Lamellar: thickening on tangential walls.Angular: thickening on angles between the cells.

Lacunar: thickening on walls facing the intercellular spaces.

Occurrence:

1 -Under epidermis of stems.

2 -Cortical tissue and pericycle of leaves.

Function :

They are plastic tissue used for mechanical support of soft plants.

sclerenchyma

They are dead cells when mature with thick secondary walls, they are elastic tissue used for mechanical support. Sclerenchyma has two types; fibres and sclereids.

A- Fibres

They are dead cells have pitted walled with narrow Lumina and pointed apices, xylary fibres are lignified while extraxylary fibres may be lignified or non-lignified.

B- Sclereids

They are dead cells short, isodiametric, elongated or branched thick walled, pitted, lignified with branched lumina.

Vascular system in the plantPlants have two different types of 'transport'

tissue Xylem and phloem. Both xylem and phloem are the vascular system.

Xylem transports water and solutes from the roots to the leaves, phloem transports food

from the leaves to the rest of the plant.

Xylem

Xylem tissue : Water and mineral transport from roots to aerial parts (leaves) of the plant

Xylem consists of : Tracheary elements . Tracheids . Vessels . Xylem fibers . Xylem parenchyma .

1 -VesselsEach vessel is formed from a series of vessel elements jointed end by end, 2ry wall is deposited in different forms:

a- Annular: 2ry wall deposits as rings in narrow vessels.

b- Spiral: 2ry wall forms a spiral in slightly wider vessels.

c- Reticulate: 2ry wall forms network.d- Sclariform: 2ry wall has elongated pits in vertical series.e- Pitted: 2ry wall is pitted and is formed in wider vessels.

Functions: vessels are used for transport and mechanical support .

2 -TracheidsGymnosperms have tracheids only but in angiosperms the xylem consists of tracheids and vessels.The tracheids are shorter than vessels and have bordered pits on their common walls.The function of tracheids is water transport and mechanical support.

5 -Phloem

Phloem is the food conducting tissue which is formed of four elements; sieve elements, companion cells, parenchyma and fibres.

Phloem tissue consists of : sieve elements : sieve cells . sieve tube . companion cell . Phloem parenchyma . Phloem fibes .

1 -Sieve elementsthese include two types:

a- Sieve cells: They are present in gymnosperms and lower vascular plants.They are long cells with tapering ends, having sieve areas on their walls.They have thin lining layer of cytoplasm, a large vacuole and they contain no nucleus.

b- Sieve tubes:They are present in angiosperms.They are arranged end by end in a long series.The common walls have sieve plate with sieve area.

The sieve pores are transversed by protoplasmic strands which connect the protoplast of neighboring sieve elements.Sieve tubes contain no nucleus.

2 -Companion cells

these are special parenchyma cells associated with the sieve tubes of dicots and monocots.A sieve tube may has one or more companion cells.The sieve tubes and companion cells are connected by plasmodesmata.A mature companion cell has a nucleus, so there is a physiological relation between it and the sieve tube.

• Functions of phloem :1)sieve tubes transport organic compounds,2)companion cells helps to regulate the metabolic activities of the sieve tube elements,3)the phloem fibres give the plant mechanical strength,4)the phloem parenchyma stores compounds such as starch.

Tissue Process What is moved Function

Xylem Transpiration Moves water and minerals from roots to leaves

والدعامة التوصيل

Phloem Translocation Moves food substances from leaves to rest of plant

التوصيل

6 -EpidermisIt occurs on the surface of plants and it is a complex tissue consisting of epidermal cells, stomata and trichomes (hairs).

Function of epidermis:1 -Protect the plant from

water loss in transpiration.2 -It acts as boundary tissue

surrounding the plant.3 -Exchange of gases

through the stomata.4 -Storage of water and

metabolic products.

1 -Epidermal cellsShape: tabular in side view, isodiametric or elongated in surface view.

Cell wall: straight, wavy walls.

Cuticle: epidermal cells are covered by an impermeable layer known as

cuticle which varies in thickness. The cuticle may be smooth as in

Stramonium or striated as in Belladonna.

The cuticle is formed mainly of cutin which is an aggregate of modified fatty acids, partly combined with

alcohols.

2 )Stomata

These are openings in the epidermis of stem and leaves. They occur in both surfaces or only on lower surface. In water plants they occur in upper surface.Types of stomata:

The types are indicated either with regard to the characters of the guard cells or with regard to the epidermal cells surrounding the stomata.

3 )Trichome

Epidermal cells are sometimes extended outwards forming projections of variable shape and size. If it is short and conical it is called papillae and the epidermis is described as papillosed e.g. Coca, but if the projections are long and well protruding they form trichomes or hairs.

The part of trichome embedded in the epidermis is called foot while the free part is the body. Hairs are classified into glandular and non-glandular or covering hairs.

Non-glandular hairs

Non

-gla

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air

s

Unicellular

Unbranched

e.g. cottony hair, cystolitic hair

Branched

e.g. Lavender.

Unbranched

Branched

e.g. Belladonna, stramonium

e.g. Calendula. e.g.Cumin.

1 -Simple branched

e.g. Tobacco.

2 -Stellate

e.g. Karkadeh

3 -Peltate :e.g. Olea

4 -Candelabrae.g. Verbascum

Glandular hairs

d- Branched stalk

c- Pluriseriate stalk

b- Biseriate stalk a- Uniseriate stalk e.g. Belladonna.

Unicellular head e.g. Mentha

Bicellular head e.g. Digitalis

Multicellular head e.g. Labiaceous hair in Mentha

clavate hair e.g. Belladonna

Un

icellu

lar

sta

lkM

ult

icellu

lar

sta

lk

e.g. Chamomile e.g. Cannabis.

e.g. Hyoscyamus muticus