WELCOME

FERTILIZATION OF ANGIOSPERMIC

PLANT

OUTLINE OF THE PRESENTATION:-

REPRODUCTION

FLOWER STRUCTRE

MAJOR EVENTS IN THE PROCESS OF SEXUAL REPRODUCTION

STRUCTURE OF STAMEN AND ANTHER

MEGASPOROGENESIS

MEGAGAMETOGENESIS

FACTOS AFFECTING FERTILIZATION

SOME IMPORTANT POINTS

REPRODUCTION• Many angiosperm species

– Reproduce both asexually and sexually• Sexual reproduction

– Generates the genetic variation that makes evolutionary adaptation possible

• Asexual reproduction in plants– Is called vegetative reproduction

Flowers

Reproductive structure of plantsComposed of four floral organs

SepalsPetalsStamensCarpels (Pistil)

• Complete flowers contain all four floral organs• Incomplete flowers lack one or more floral organs,

for example stamens or carpels• Clusters of flowers are called inflorescences

StyleOvary

CarpelStigma

Sepal

Receptacle

Petal

Filament

AntherStamen

Stamen Anther

Filament

Stigma CarpelStyle

Ovary

Anther

Pollen tube

Germinated pollen grain (n)(male gametophyte)

Ovary

Ovule

Embryo sac (n)(female gametophyte)

Egg (n) Sperm (n)

Zygote(2n)

Seed

SeedEmbryo (2n)(sporophyte)

Simple fruit

Germinatingseed

Mature sporophyteplant (2n)

(b) Simplified angiosperm life cycle

Key

Receptacle

SepalPetal

(a) Structure of an idealized flower

Haploid (n)Diploid (2n)

FERTILIZATION

Major Events In The Process Of Sexual Reproduction:-1.Microsporogenesis:-in This Process Pollen Grain Or Micro Spore Formed From Microspore Mother Cell2.Microgametogenesis:- This Involve The Formation Of Male Gametes From Microspore(pollen Grain) 3.Pollination:- This Is The Transfer Of Pollen Grains Anther To Stigma4.Megasporogenesis:- It Leads To The Formation Of Megaspores From Megaspore Mother Cell Inside The Ovule Cell5.Megagametogenesis:-involves The Formation Of Embryo Sac From Megaspore6.Fertilization:-involves Fusion Of Male And Female Gametes, resulting In The Formation Of Zygote7.Embryogeny:-involves Development Of Embryo From Zygote8.Endosperm Formation:- Includes The Formation And Development Of Endosperm As A Result Of Triple Fusion

(a)The Stamen:- Stamen in a flower consists of two parts, the long narrow

stalk like filament and upper broader knob-like bi-lobed anther .

The proximal end of the filament is attached to the thalamus or petal of the flower.

The number and length of stamens vary in different species.

b)Structure of anther:- A normal bithecous or dithecous anther is made up of two

anther lobes, which are connected by a strip of sterile part called connective.

Two anther lobes contain four elongated cavities or pollen sacs (microsporangia) in which pollen grains are produced.

A Mature Anther Is Made Up Of 1.Anther Wall And 2.Pollen Chamber1.Wall:- A) Epidermis:-outer Most Layer And One Cell Thickness B) Endothecium:- Next To Epidermis, Single Layer With Radial Elongated Cell With Fibrous Thickening That Helps In Dehiscence.In These Cell Some Cell Are Present Without Thickening Called Stomium. C) Middle Layer:- 3-4 Layers Of Thin Walled Cell Situated Just Below Endothecium Called As Middle Layer. It Is Disintegrated At The Time Of Anther Matured D) Tapetum:- inner Most Layer. Multinucleate Densely Cytoplasmic Cell.Provide Nutrition To Developing Microspore. It Is Of Two Type,i.e.i. Secretory Or Glandular:-remain In Contact With Anther Wall Throughoutii. Amoeboid Or Plasmodial Tapetum:-the Cell Of It Separate Form The Wall

And Move Freely In The Pollen Chamber2. Pollen chamber:-It forms the central cavity of the anther lobe. Microsporogenesis takes place here.

DEVELOPMENT OF ANTHER:-

Microsporogenesis- two type of cytokinesis

Microsporogenesis-different type of microspore tetrads

(a) Development of a malegametophyte (in pollen grain)

Microsporangium(pollen sac)

Microsporocyte (2n)

4 microspores (n)

Each of 4microspores (n)

Malegametophyte

Generative cell (n)

MEIOSIS

Ragweedpollengrain

Nucleus oftube cell (n)

MITOSIS

20 µm

75 µm

Different stages of micro gametogenesis.

(SPOROPOLLENIN)

1. MEGASPOROGENESIS:-

DIFFERENT MEGASPORE DEVELOPMENT

A. Tenuinucellate ovule , B. Crassinucillate ovule

2. MEGAGAMETOGENESISIt is the process of development of female gametophyte or embryo sac from megaspore mother cell.Development of embryo sac (female gametophyte):-On the basis of their development following 3 types embryo sacs are seen such as:-i) monosporic , ii) bisporic , iii) tetrasporic In development of typical monosporic embryo sac only one out of the 4 megaspore takes part other degenerate. A monosporic 8 – nucleate embryo sac called as pollygonum type, occure in 70% of angiosperms

B C

synergids show a filiform apparatus that attract and guide the pollen tube.

Thus a matured pollygonum type of embryo sac at the time fertilization is 7-celled

Ovule

(b) Development of a femalegametophyte (embryo sac)

Megasporangium (2n)

Megasporocyte (2n)

Integuments (2n)

Micropyle

MEIOSIS

Survivingmegaspore (n)

3 antipodal cells (n)

2 polar nuclei (n)

1 egg (n)

2 synergids (n)

Female gam

etophyte(em

bryo sac)

Ovule

Embryosac

Integuments (2n)

MITOSIS

100

µm

(a)

Development of a malegametophyte (in pollen grain)

Microsporangium(pollen sac)

Microsporocyte (2n)

4 microspores (n)

Each of 4microspores (n)

Malegametophyte

Generative cell (n)

Ovule

(b) Development of a femalegametophyte (embryo sac)

Megasporangium (2n)

Megasporocyte (2n)

Integuments (2n)

Micropyle

MEIOSIS

Survivingmegaspore (n)

3 antipodal cells (n)

2 polar nuclei (n)

1 egg (n)

2 synergids (n)

Female gam

etophyte(em

bryo sac)

Ovule

Embryosac

Integuments (2n)

Ragweedpollengrain

Nucleus oftube cell (n)

MITOSIS

100

µm

20 µm

75 µm

Growth Of Pollen Tube And FertilizationPollen grain

Pollen tube

ovary

ovulePollar nuclei

Egg apparatus

2 sperm

Tube nucleus

style

micropyle

Entry of pollen tube in the ovule:-

Porogamy Chalazogamy Mesogamy

Ovule

Polar nuclei

Egg

Synergid

2 sperm

If a pollen grain germinates, a pollen tube grows down the style toward the ovary.

One sperm fertilizes the egg, forming the zygote. The other sperm combines with the two polar nuclei of the embryo sac’s large central cell, forming a triploid cell that develops into the nutritive tissue called endosperm. This is called as triple fusion and double fertilization

The pollen tube discharges two sperm into the female gametophyte (embryo sac) within an ovule.

Endospermnucleus (3n)(2 polar nucleiplus sperm)

Endospermnucleus (3n)(2 polar nucleiplus sperm)

FACTOS AFFECTING FERTILIZATION:- 1)Pollinating agent:-

A) Wind (anemophily)

B) Water (hydrophily)

C) Insects (entomophily)

D) Birds (ornithophily)

2) Male sterility

3)Self incompactibility

4)Vaibility of pollen grain

5)Avaibility of nutrient in growing pollen tube

6)Receptivity of stigmatic surface

Flower Parts Mature Structure– Egg + sperm = zygote Embryo– 2 Polar nuclei + Sperm Endosperm– Integument Testa (Seedcoat)– Nucellus Perisperm– Micropyle Micropyle– Funiculus Hilum– Ovary Wall Pericarp (fruit)– Ovule Seed– Ovary Fruit

SOME IMPORTANT POINTS

THANK U

SANDEEP KUMAR SINGHM.SC. 1ST. YEARDPT.-BOTANY(G.P.B.)DR.P.D.K.V.,AKOLA