Botany Lecture 3

8/12/2019 Botany Lecture 3

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Spring Semester 2013

Botany

and Medicinal Plants

Department of PharmacognosyP ro f . Na h l a AyoubLec tu re 3 )

1

Pl nt cell


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Lecture Content

Pl nt cell I- Cell wall

1. Cellulose wall

2. Lignified wall

3. Suberinised &cutinised wall

4. Mucilagenous wall5. Chitinous wall

II-Different types of plant cells

1. Parenchymatous tissue

2. Collenchymatous tissue

3. Sclerenchyma (support cells)

Sclereids

Fibres

4. Vascular Tissue

Xylem Phloem

5. Secretory Tissue

secretory cell

Secretory cavities

Schizogenous

Lyzogenous

Schizo-

lyzogenous

Latex tissue


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Pl nt cell

I- Cell wall


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Cellulose, hemicellulose and pectin may be

present in the cell wall

Cellulose is the most abounded carbohydrates;

it form 50% or more of all the carbon in plants.

Detection

Cellulose+ iodine no bluecolor

Hemicellulose + iodine bluecolor

1. Cellulose wall

Cellulose: Polymer of glucose

(Plant fiber)
http://upload.wikimedia.org/wikipedia/commons/0/07/Cellulose_Sessel.svg


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2. Lignified wall

Complex polymer ofphenolic compound

Cell wall of tracheids,vessels, fibers andsclereids

Lignified wall+phloroglucinol and HClgives red color

3. Suberinised &

cutinised cell wall

-Suberin& cutinare glycerolesters of some acids as suberic

acids.

-These material water proof

cells.

-Suberinis found in cork cell

and endodermal cell

-Cutincovers the epidermal cellof the leaves, which may show

papipllae, ridges and striation.

Cutin and suberin + suddan IIIred color


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1,6-hexanedicarboxylic acid

Subric acid (Covers the cork)

Cutin (Covers the

epidermal cells)

Papipllae


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4. Mucilagenous wall

5. Chitinous wall

-Cell wall is converted in some

cases intomucilage and gum

-Polysaccharide complexes ofsugar and uronic acid.

mucilage + Rhuthenium redred color

- Chitinforms the major part of

insect cell wall

-Chitin + 0.5% solution of iodinein potassium iodide then with

sulphuric acid.

violet color


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Pl nt cellII-Different types of plant

cells


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Leaf Anatomy
http://www.nationmaster.com/encyclopedia/Image:Leaf-anatomy.svg


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Leaf Anatomy


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vascular system

Stem Anatomy


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Dicot stems

Dicot stems have pith in the center, with vascular bundles forming a distinct ring. The outside ofthe stem is covered with an epidermis, which is covered by a waterproof cuticle. The epidermis

also may contain stomata for gas exchange. A cortex of parenchyma cells lies between theepidermis and vascular bundles.


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Vascular bundles are present throughout the monocot stem, although

concentrated towards the outside.

Monocot stems


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Root Anatomy

The Root Tip

Meristem- a region of

rapid mitosis, which

produces the new cells

for root growth.

Root cap- a sheath of

cells that protects the

meristem from abrasion

and damage as the

root tip grows through

the soil.

The Region of

Elongation

The cells produced by

mitosis undergo aperiod of elongation in

the direction of the axis

of the root. It is at this

time that they are

sensitive to gravity and

respond withgravitropism .


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1-Parenchymatous tissue

Occurrence: in various

parts of plant e.g. pith,cortex..& mesophyll of

the leaves.

Characters: isodiametric,

polygonal or rounded cell ,

cellulosic wall & may be

lignified and pitted

parenchyma

2-Collenchymatous tissue

Collenchyma is a living tissue

derived from parenchayma

with greater mechanical

strength showing thick wall

composed of cellulose.

Occurrence:the mechanical

tissue of the herbaceous stem

& of the petioles and the

midribs of the leaves

Characters: The cells are

usually 4 to 6 sided in

transverse section, axially

elongated in longitudinal

section


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1-Parenchymatous tissue

2-Collenchymatous tissue

Cellulosethickening


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3. Sclerenchyma (support cells)

Thick secondary cell walls (showing simple pitting)

Dead at functional maturity

Can not increase in length - occur in parts of the

plant which have quit growing in length

Two types: sclereids and fibres


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3. 1.Sclereids (Stone cells):

Occurrence: in hard outer coat of the

seeds, fruit, bark and the pericyclicregion (located between the endodermis

and phloem of the root).

Characters:isodimetric in shape. Thewall of the stone cells is thick,

lignified&may show well-marked

striation.

The cell lumens are small, sometimes

containing some diagnostic elements

e.g. prisms of calcium oxalate, or

starch granules.


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3.2. Fibers

Occurrence:in xylem, pericycle and phloem.

Characters:Spindle-shaped or elongated cells with

pointed ends known as prosenchyma.

The cell wall may be composed of cellulose or may

show some degree of lignifications.

Most mature fiber are unicellular.


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Fibers


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4-Vascular Tissue

There are two types ofvascular tissue: xylem

and phloem.

Vascular tissue may be

scattered in ground

tissue or regularly

arranged forming a

ring.


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Xylem conducts water from soil to leaves.

composed of sieveconducting tissuenutrient-Phloemtube or sieve cells mixed with parenchyma and fibers.

phloem transports organic molecules (particularlyThe

sugars) to wherever they are needed.

is the only part of a woody stem whereThe cambiumoccurs.cell division

It contains undifferentiated cells that divide rapidly toto the inside and secondaryxylemproduce secondaryto the outside.phloem

Vascular Tissue


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A- Xylem

Xylemconducts waterfrom soil to leaves. The primary xylem is composed of protoand meta-

xylem.

Thickening occurs in the stem and root by formation

of secondary xylem.

The structural element of xylem are Xylem Tracheids: pitted elongated cells allow water to pass from one

to another

Xylem Vessels: the fundamental conducting elements of xylem

Xylem Parenchyma: storage tissue.

Xylem Fibers: Sclerenchyma fibers providing mechanical support to

the essential elements.


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Xylem Components (Tracheid, Vessels, Parenchyma and Fibers)

Tracheid

XylemVessel

Tracheid

Parenchyma


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Different Types of Xylem Vessels

Annular vessels :rings placed more or less at equal distance from each other.Spiral vessels : Helix or coil.Scalariform vessels : cross bands resembling the steps of a ladder.Reticulate vessels: irregular and appear in the form of a network.Pitted vessels : in which the secondary thickenings result in the formation of

depressions on the primary wall called pits.

Secondarythickenings


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sclariform

.Different Types of

Xylem Vessels:

annular

spiralreticulate


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Xylem Tracheid Xylem VesselXylem Tracheae

Xylem

parenchymacells

More primitive Pits allow water to

pass from one to

another

Less efficient at

conducting water

More like a fiber

Four typesannular, spiral,

reticulate and

sclariform.

Fundamentalconducting elements

of xylem.

Vessels are derived

from vertical series ofcells, dissolution of the

wall give continuous

tube.

Fourtypes of vessels.annular thickening of

the stem and root).

Spiral, sclariform

and reticulate.

Axiallyelongated,

sometimes thin

walled but often

with walls

showing

thickeninig and

lingification.

Xylem

parenchyma

function as

storage tissue.


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B- Phloem

Phloem is the food conducting tissue.

The phloem elements include sieve tubes, companioncelland phloem parenchyma

The sieve tubesformed from vertical series of

elongated cells interconnected by perforation in theirwalls in areas known as sieve plates.

The companion cellis intimately associated with

sieve tube structurally and functionally. Thecompanion cell is characterized by its dense protoplastand well developed nucleus and by thin cellulose wall.

The phloem may contain secretory cells
http://www.sbs.auckland.ac.nz/uoa/fms/default/science/about/departments/sbs/student_information/schools/nzplants/concepts/phloem_stern2(316).jpg


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Phloem
http://www.sbs.auckland.ac.nz/uoa/fms/default/science/about/departments/sbs/student_information/schools/nzplants/concepts/phloem_stern2(316).jpghttp://www.sbs.auckland.ac.nz/uoa/fms/default/science/about/departments/sbs/student_information/schools/nzplants/concepts/phloem_stern2(316).jpg


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Diagram showing the cross sections of a xylem and a phloem


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5. Secretory tissue

Secretorycavities

Schizogenous

Latex tissue

secretory cells

Lyzogenous

Schizo-lyzogenous

The vittae

Latex cells Latex vessels


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5. Secretory tissue Oil cells: occur in Cinnamon, Cassia and Ginger.

Secretory cavitiesor glands may be :

1. Schizogenous:arises by separation of cell andsubsequent formation of a secretory epithelium e.g.Eucalyptus.

2. Lyzogenous: formed by breakdown of the cell

forming a cavity not bounded by definite epitheliume.g. inGossypium.

3. Schizo-lyzogenouscavities occur in Rutaceae.


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Schizogenous Lysigenous Schizo-lysigenous

arises by separation of

cell and subsequent

formation of asecretory epithelium

formed by breakdown

of the cell forming a

cavity not bounded bydefinite epithelium

Initially schizogenous

but lysigeny occurs in

cavities in later stagesas the epithelium cells

lining the space

undergo autolysis

further enlarging thespace.


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Solid mass of

secreting cells

Formation of central cavity

By gradual disintegration of

cells starting from centre

Lyses of walls and

secretion

poured in the cavity

Lysigenous gland

Schizogenous gland

Epithelial cells secreteproducts in the cavity

Formation of central cavityBy separation of cells


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Latex tissue consist of latex cells or latex

vessels. Latex cells

Latex vessels: formed by partial or complete fusion of a

longitudinal series of cells.

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Botany Lecture 3