DEPARTMENT OF BOTANY

ANCILLARY BOTANY

I YEAR – II SEMESTER COURSE CODE: 7BBOA2

ALLIED COURSE II – TAXONOMY OF ANGIOSPERMS, ECONOMIC

BOTANY AND EMBRYOLOGY OF ANGIOSPERMS

Unit I Taxonomy of Angiosperms

1. Aim and significance of Taxonomy

2. Herbarium techniques

3. Outline of Benthem and Hooker of classification.

Unit II Families

a. Annonaceae

b. Rutaceae

c. Anacardiaceae

d. Asclepiadaceae

e. Euphorbiaceae

f. Poaceae

Unit III Economic Botany

Cereals – Maize & Ragi

Pulses – Green Gram & Soyabean

Fruits – Pomegranate & Mango

Beverages – Coffee & Cocoa

Fibres – Jute & Cotton

Resins and Gums – Canada Balsam & Turpentine

Essential Oils – Sandal oil & Olive Oil

Wood – Rose wood & Bamboo

Unit IV Embryology of Angiosperms

Structure of anther and male gametophyte, Different types of Ovules, Structure and

development of embryo sac (Polygonum type)

Unit V

1. Fertilization – double fertilization, syngamy-significance

2. Different types of endosperm(Nuclear, cellular, helobial)

3. Structure and development of dicot (Capsella) and monocot embryo(Lazula).

PLANT TAXONOMY

Plant taxonomy is the science that finds, identifies, describes, classifies, and

names plants.

It is also known as systematic botany

It helps to identifiy and name various plants on the earth.

AIM AND SIGNIFICANCE OF PLANT TAXONOMY

To know all plants on the earth with their names

To build up a reference system for plants for easy identification , naming and

classification

To understand the facts of evolution of different plants

To give every plant an universal name to avoid confusions in naming of plants.

PLANT NOMENCLATURE

Naming of plants is known as nomenclature

It was first introduced by Linnaues In 1753

Naming of plants by two words is called binominal nomenclature

The starting letter of genus should be in capital letter

Species name should be in small letter.

Binomials are mostly in greek or latin name.

Eg. Mangifera indica.

ADVANTAGES OF BINOMIAL NOMENCLATURE

1. Binomial names are universal

2. They are definite and precise

3. The names themselves describes the main features of the plants

4. Binomial helps to arrange the plants according to the systematic

relationship.

INTERNATIONAL CODE OF BOTANICAL NOMENCLATURE (ICBN)

HERBARIUM TECHNIQUES

Herbarium is a collection of dried specimen of plants mounted on herbarium

sheets.

The individual sheets of the herbarium are known as herbarium specimens.

Herbarium was first made by Cesalpini in 1550.

Each herbarium specimen contains number and description of the plant.

It consists of a three part process

collecting the plant material,

pressing & drying

mounting.

BASIC TOOLS FOR HERBARIUM TECHNIQUES

Plant press

Plastic bags

Chopper

Garden trowel

Small note book & pencil

Labels and tags

Camera

GPS & altimeter

Binocular

Drying sheets

Plant Specimen

Drying sheets

COLLECTION OF PLANT MATERIAL

Specimens are collected usually at the time when they have flowers and fruits.

Two or three specimens are collected.

The collection number of the specimen entered in the field note book is given to

the collected specimen.

This is done by entering a number on a label and tieing it into the specimen.

After labeling, the specimens are put inside the vasculum or polythene bags.

PRESSING

After collection, the unwanted parts of the plants are removed .

One or two drying sheets are spread on a flat ground.

One specimen is placed on the sheets and leaves, flowers are spread with fingers.

Another two drying sheets are kept above

Another specimen is kept over the drying sheets

This is done until it reaches 1½ feet.

One board of the plant press is kept below the drying sheets and another above the

drying sheets.

DRYING

On the next day, the bundles are opened and the wet sheets are replaced by new

one

They are tied and exposed to the sunlight

They are shade dried and stored.

This is followed for one week.

DDT powder may be applied over the half dry specimens

The dried specimens may be damaged by small insects

Mercuric chloride is used for this purpose.

MOUNTING

The dried specimens are mounted on thick white boards called herbarium sheets.

The sheet should be 11½ “ wide and 16” long.

They are prepared from high quality paper.

At lower right hand corner, there is a printed label to write down the particulars of

the specimen.

The specimen is placed on a paper on its upper surface and gums on lower

surface.

A drying sheet is placed over the specimen and some weight is kept over the

specimen.

LABELING

All the relevant details are filled in the herbarium label

The label should contain the following details

STORAGE:

The arranged herbarium sheets are maintained in herbarium cases.

It will have three to five shelves.

They are placed in herbarium house.

DDT or carbon tetrachloride and ethylene dichloride is used to protect the

herbarium specimens.

USES OF HERBARIUM TECHNIQUES

It shows individual variations and evolution patterns of plants

It can be used as teaching aids

It is helpful for plant identification

It helps to match with a new plant

It is used for proposing new system of classification

It provides complete information about wild, cultivated and introduced plants and

their uses.

BENTHAM AND HOOKER SYSTEM OF CLASSIFICATION

Bentham and Hooker classified the plants based on natural characters.

He classified the plants in the book called Genera Plantarum (1862-1883).

It is a classification of only seed plants.

Merits:

1) It is simple and easy to use for practical purpose.

2) Every genus and species were studied from the actual specimens

3) Ranales is placed first in the dicot which is very reasonable.

4) Monocots followed dicots

5) Gymnosperms were treated by Bentham and Hooker as a third taxon and

placed between Dicots and Monocots

Demerits:

1) Placing of Gymnosperms between dicot and monocot is not accepted.

2) Artificial characters are considered here and there.

3) Monochylamydeae is considered to be the most highly evolved among

polypetalae is the most primitive groups among dicots

4) Some of the related orders are widely separated from each other.

5) There is no uniformity in the arrangement of groups.

6) In the classification of monocotyledon, importance is not given to all

natural characters.

ANNONACEAE

Class: Dicotyledons

Sub class: Polypetalae

Series: Thalamiflorae

Order: Ranales

Family Annonaceae

Distribution: Mostly tropical

Habit: Trees eg. Polyalthia longifolia, Annona squamosa.

Some are woody climbers eg. Artabotrys odoratissimus

Leaves: Simple, alternate, stipulate, petiole is small and wavy margin is seen.

Inflorescence: Usually solitary, axillary or terminal. Umbel in Polyalthia.

Flowers:

Complete, bisexual, regular, actinomorphic, rarely unisexual, hypogynous.

Calyx: 3 Sepals, free, sometimes slightly fused. Valvate aestivation.

Corolla: Petals 3 or 6. Polypetalous. Three petals in Annona. Petals are thick and fleshy,

valvate or imbricate aestivation.

Androecium:

Stamens are free, thick, bearing dithecous (bilobed) anther. The anther is terminated by

an elongated hood like connective.

Gynoecium:

Ovary superior, unilocular and marginal placentation.

Pollination : Entomophilous

Fruit: Aggregate

An aggregate fruit develops from a single flower. In Annona, each carpel after

fertilization fuses together and form a single fruit.

Economic Importance:

1. The fleshy fruits of various species of Annona are edible. Eg. Annona squamosa,

2. Flowers of Artabotrys are sweet smelling, hence they are grown in gardens

3. Polyalthia longifolia are ornamental trees and are grown in parks.

4. The wood of Polyalthia fragans is used for making cricket stumps.

5. Oil is extracted from the seed of Annona reticulata is used in insecticides and

soap making.

RUTACEAE Class: Dicotyledons

Sub class: Polypetalae

Series: Disciflorae

Order: Geraniales

Family Rutaceae

Distribution: They are widely distributed in warm temperate regions, also found

in tropical regions.

Habit: Generally shrubs or trees.

Eg) Murraya exotica- an ornamental shrub with scented flowers

Aegle marmelos ( Vilvam): It is a tree.

Leaves: Simple or compound. Usually alternate, exstipulate, gland dotted. The

glands contain volatile oil which give typical smell to the leaves. In Citrus

species, the leaves possess winged petioles, unifoliate compound leaves.

Inflorescence:

Generally it is cymose ( mostly dichasial cyme). Sometimes racemose

Flower:

Pedicellate, complete, mostly bisexual, regular, actinomorphic. Sometimes the

flowers are unisexual eg. Zanthoxylum. hypogynous.

Calyx;

5 sepals, free, polysepalous. Aestivation Imbricate or valvate.

Corolla:

4 or 5 petals. Polypetalous. Gamopetalous in some case. Disc is present between

corolla and ovary. Imbricate aestivation.

Androecium;

Usually ten or eight stamens. In Murraya exotica, ten stamens are arranged in two

whorls of five each. Stamens are present in Obdiplostamenous condition.

(5 stamens opposite to sepals and 5 opposite to petals). Anthers are dithecous,

introse, basifixed.

Gynoecium:

Carpels generally 3 to 5 or polycarpellary. Syncarpous, superior ovary. Mostly

ovules on axile placentation. Each locule contains one or more anatropous ovules.

Pollination: Entamophilly

Fruit: Usually Hesperidium

Economic importance:

1) Citrus aurantium - lime

2) Citrus sinensis - sathukudi

3) Citrus limnia - lemon

4) Citus reticulate – Kamala orange

5) Feronia elaphantum- Vilampalam

These are used as fruits and food.

The pulp of the fruit of Aegle marmelos is used as medicine for dysentery.

Zanthoxylum fruit is used to relieve toothache.

The leaves of many Citrus species yields oil.

Murraya keonjii is used in cooking as curry leaves.

FAMILY ASCLEPIDIACEAE

Class : Dicots

Subclass: Gamopetalae

Series : Bicarpellatae

Order : Gentianales

Habit: Here all forms are present

Herb : Ascleipias

Shrub : Calotropis

Twiner: Daemia extensa

Xerophyte: Caralluma

Epiphyte : Dischidia sps.

Leaves:

Simple leaf, opposite and decussate. Each pair of leaf is arranged at right

angle to one another. Each leaves is covered by with waxes alone the stem and leaf

latex (milky fluid.

Inflorescence: Umbel.

Flower:

Bracteate, Bisexual, actinomorphic, tetra or pentamerous, hypogynous.

Calyx:

It has 5 sepals free (polysepalous) ( Embrical aestivation).

Corolla:

Has 5 petals united (Gamopetalous) along the petals, there are hair like out

growth called Corolline corone

Androecium:

5 stamens. Each stamens is attached with a petals. This condition is called

epipetalous stamens. All the filaments are fused together to form tube like

structure namely Staminal tube. Anthers are dithecous. Stamens are adnate to the

gynoecium to form the gynostegium.

Translator in Asclepidaceae:

The pollen grains are aggregated in a single mass called pollinia. Two such

pollinia are united together by means of a stalk called caudicle. The caudicles

attached to a dark brown body called carpusculum. The carpusculum is situated

in a slit at the five corners of the pentagonal stigma.

Gynoecium:

Bicarpellary, apocarpous superior. Carpels are separated at the base and

united at the stylar region ending in a single pentagonal stigma.

Fruit:

Generally it is a pair of follicles.

Seed: Cosmose.

Economic importance:

Calotropis gigantea: The seeds are used for stuffing purpose. The stem

yields a fibre.

Ceropegia hirsuta: the tubers are edible.

Daemia extensa: The juice of leaves is used as the remedy for Diarrhoea,

asthma

Hemidesmus indicus : the roots are used as a tonic to increase appetite, and

as a remedy for fever, skin disease, snake bite, rheumatism.

EMBRYOLOGY

STRUCTURE AND DEVELOPMENT OF ANTHER:

Anther is the part of stamen, enclosing the pollen grains or microspores.

Stamen consists of two parts namely a filament and anther.

The pollen grains develop from the sporogenous tissue of the archesporium

The sporogenous cell develop into the primary parietal layer

The primary parietal layer undergoes a series of periclinal and anticlinal

divisions

In the mature anther, the wall is formed of Epidermis, Endothecium,

Middle layers and Tapetum.

STRUCTURE OF MATURE ANTHER:

a) Epidermis:

It is the outermost layer of the anther.

It consists of a single layer of cells

it is compactly arranged.

The cells of the epidermis undergo anticlinal division.

Epidermis is protective in function.

b) Endothecium:

It is the second layer of anther wall.

It is also known as fibrous layer.

It consists of fibrous bands.

It consists of single layer of radially elongated cells

Fibrous band is made up of lignin.

The endothecial layers become hygroscopic due to the development

of fibrous band.

It helps in dehiscence of pollen grains.

c) Middle Layer:

It is third layer of the anther wall lying below the endothecium.

It consists of two or three layers of thin walled parenchyma cells.

The cells store starch grains.

d) Tapetum:

It is the inner most layer of the anther wall.

It is formed of a single layer of cells surrounding the sporogenous

tissue.

The cells are large, radially elongated and contain dense cytoplasm.

It is a nutritive layer for the developing microspores.

The cells of the primary sporogenous layer derived from the

archesporium directly function as pollen mother cells.

TAPETUM:

It is the inner most layer of the anther wall.

It is formed of a single layer of cells surrounding the sporogenous

tissue.

The cells are large, radially elongated and contain dense cytoplasm.

It is a nutritive layer for the developing microspores

Based on its behavior, tapetum is of two types,

Glandular or secretory tapetum

Amoeboid or plasmodium tapetum

Glandular tapetum:

The tapetal cells remain intact in their original position throughout

the development of microspores.

The tapetal cells do not degenerate.

The cells become rich in protoplasmic contents and secrete a

plasmodium that surrounds the pollengrains.

The secreted plasmodium contribute a material known as

sporopollenin

It helps in thickening of the exine of pollen grains.

Amoeboid tapetum:

In this type, the inner and radial walls of the tapetal cells break down

and the protoplast becomes a plasmodial mass.

This plasmodium mass called tapetal periplasmodium.

This periplasmodium in which the pollen mother cells are

suspended.

FUNCTIONS OF TAPETUM:

Tapetum is a nutritive tissue. It serves for the nutrition of the pollen

grains or microspores.

It plays an important role in the pollen wall formation.

The plastids of the tapetal cells synthesize materials like pollenkit.

It forms channel for the transport of materials to reach the pollen

mother cells.

Tapetal cells store nutrients.

STRUCTURE AND DEVELOPMENT OF MALE GAMETOPHYTE

Pollengrain consist of a wall, cytoplasm and nucleus.

The wall of the pollengrains is formed of two layers.

The outer layer is exine

The inner layer is intine.

The exine is thick, outer protective covering.

The exine layer is made up of sporopollenin

The intine layer is the thin and uniform inner layer.

The pollen grain contains dense cytoplasm and a prominent nucleus.

It consists of proteins, fats, carbohydrates, vitamins etc.,

DEVELOPMENT OF MALE GAMETOPHYTE:

The pollen grain undergoes first mitotic division to form two unequal cell.

The larger one is known as vegetative cell.

The smaller one is known as generative cell.

Now, the generative cell gets detached from the wall and becomes

spherical.

Generative cell is smaller than the vegetative cell.

The intine of the pollen grain protrudes through one of the germpores.

A pollen tube is formed.

The vegetative and generative cells of the pollen grains migrate into the

pollen tube..

The vegetative nucleus moves inside the tube. This tube is known as tube

nucleus.

Now, the generative cell divides mitotically to form two male gametes.

During fertilization in the embryosac, one of the sperms fuses with the egg

to form zygote.

STRUCTURE OF OVULE:

The ovule consists of two parts namely nucellus and embryo sac.

The ovule consists of a central mass of homogenous tisuue knaoen

as nucellus.

The nucellus is surrounded by outer and inner integuments.

There is a opening at the tip of the ovule called as Micropyle.

The two integuments join at the base of the nucellus to form a

chalaza.

The embryosac develops in the nucellus of the ovule towards the

micropyle.

TYPES OF OVULE

There are six types of ovule:

1. Orthotropous ovule

2. Anatropous ovule

3. Campylotropous ovule

4. Hemianatropous ovule

5. Amphitropous ovule

6. Circinotropous ovule

Orthotropous ovule

It is an erect ovule.

The body of the ovule is upright. (Ortho = straight)

The funicle lies on the same straight vertical line.

Anatropous ovule:

It is an inverted ovule.

The micropyle comes nearer to the funicle and hilum.

The chalaza is at the opposite end of the ovule.

Campylotropous ovule:

It is a curved ovule ( Campylo = curved)

The micropyle and funiculus lie in parallel lines.

Hemianatropous ovule:

It is an t-shaped ovule.

The micropyle and chalaza remain at right angles to the funicle.

Amphitropous ovule:

The ovule is like a horse-shoe shaped. (Amphi = on both sides).

The embryosac bends like a horse shoe shaped.

Circinotropous ovule:

The funicle is very long and forms a complete circle.

The ovule curves completely and the micropyle again points upward.

Development of female gametophyte:

It is otherwise known as embryo sac.

The nucleus of the functional megaspore enlarges in size and undergoes

first mitotic division to for two nuclei.

The two nuclei move in opposite directions.

At each pole, the nucleus undergoes division to form four nuclei.

The embryo sac elongates and the cellular organization occurs in the

embryosac.

Three nuclei organize into the egg apparatus and the remaining one nucleus

form upper polar nucleus.

Three nuclei organize into three antipodal cells and the remaining one

nucleus forms lower polar nucleus.

The two polar nuclei move to the centre of the embryo sac and fuse.

Synergids

Egg cell

Polar nucleai

Antipodals

Structure of female gametophyte: (embryo sac)

It consists of an embryo sac wall, an egg apparatus , central cell and

antipodal cell.

The egg apparatus lies at the micropylar end of the embryo sac.

It consist of an egg cell and synergids.

The synergids are found on either side of egg cell.

Filiform apparatus is found on the synergids. It is secretory and protective

in function.

The antipodals are found on the chalazal end. They degenerate after

fertilization.

The two polar nuclei present at the centre of the embryo sac is called

central cell or secondary nucleus.

DOUBLE FERTILIZATION

The fusion of male gametes with the females gametes is known as

Fertilization.

The fusion of one male gamete with the female gamete followed by the

fusion of second male gamete with the polar nuclei.

The fusion of the first male gamete with the female gamete produces the

zygote.

The fusion of the second male gamete with the polar nuclei produces the

endosperm.

It was first discovered by Nawaschin in 1918.

STEPS:

The pollen grain develops into pollen tube.

The tip of the pollen tube is known as cap block.

The tube enters into synergid area.

The tip of the pollen tube breaks and the contents of the pollen tube are

discharged.

The two male gamets or sperms released by the pollen tube.

One fuses with the egg and other male gamete fuses with the polar nuclei.

Since there are two fertilizations occurring. It is known as double

fertilization.

Second male gamete fuses with the two polar nuclei. Hence it is known as

triple fusion.

Significance:

The embryo is formed from the fertilized egg.

Endosperm is formed from the fertilized polar nuclei.

The double fertilization is responsible for production of viable seeds.

DICOT EMBRYO

Structure:

An embryo is rudimentary plant formed in the seed.

The dicot embryo has an

o embryonal axis,

o two cotyledons,

o an epicotyls,

o a hypocotyls,

o a plumule,

o a radical

o suspensor

The cotyledons are massive, plate like, curved and lateral

The embryonal axis is short.

Epicotyl and hypocotyls is present above the cotyledon.

When the seed germinate, the plumule becomes the shoot system

The radical becomes the root system.

The radicle end of the embryo is connected to the micropylar end of

embryo sac by a suspensor.

Development of dicot embryo – crucifer type:

This type of embryo development is seen in capsella sp.

The zygote enlarges in size. It divides transversely to form unequal

two cells.

The upper large cell is towards the micropyle is known as basal cell

and the lower cell is known as terminal cells. This is known as two

celled stage.

The basal cell divides transversely to form two cells. This is known as

four cell stage.

The two cells of the terminal cell undergo another vertical division to

form quadrant stage.

The four cells of the quadrant cells undergo transverse division to

form eight cells.

The lower 4 cell develops into two cotyledons and stem tip. The upper

4 cells divide and form the root.

These cells divide and forms suspensor. This suspensor serves as

haustorium.

ENDOSPERM

Endosperm is a nutritive tissue for the embryo stored in the seed

It is formed by the fusion of one male gamete and with the polar nuclei

It is of three types

ENDOSPERM

Nuclear Cellular Helobial

NUCLEAR

CELLULAR

HELOBIAL

NUCLEAR ENDOSPERM

The division of the primary endosperm nucleus and its further divisions are not

followed by wall formation

All the nuclei remain free in the endosperm

Ex ample is oxyspora

In Coconut, the endosperm is nuclear type

The free nuclei float in the fluid of the embryo sac.

At a later stage, the fluid shows several cells.

These cells slowly settles at the side.

CELLULAR ENDOSPERM

The division of the primary endosperm nucleus are followed by immediate wall

formation.

Free nuclear stage is absent.

Haustoria is commonly seen.

Example is Magnolia.

HELOBIAL ENDOSPERM

It is an intermediate type

It is seen in monocots.

The primary endosperm nucleus moves to the chalazal end of the embryo sac and

divides into two.

The cell wall formation occurs in the micropylar chamber.

The haustoria are produced by the endosperm for the absorption of food.