Angiosperm Development and Reproduction

1. Shri Shivaji Arts Commerce & Science College
Motala
Embryology of Angiosperm
Presented By
Mr. Shubham S. Sakhare
Assistant Professor
Department Of Botany

2. Structure of Flower
• Flower consist of four whorls namely – Petals,
Carpels, Sepals and Stamen.
• Sepals is the outer whorl of flower.
• Petals is the inner whorl of flower.
• The Androecium is a male Reproductive Structure.
• Androecium consist of anther, filaments and
connective.
• Anther holds Male Gamete, Pollen grains.
• While Gynoecium is a female reproductive
structure.
• The Gynoecium consists of carpels comprise of
Style, Ovary & stigma.

3. Microsporangium
 Stamen is a male reproductive organ
 Consists of filament anther connective
 Anther present at tip of filament
 Sterile middle part of the anther is called as connective
 Each anther contain two lobes and each lobe is divided into two sacs or
microsporangia
 Thus single anther is made up of four pollen sac and described as
tetrasporangiate.

4. Structure of Anther
Mature Anther wall made up of four layers
1) Epidermis : Outermost layer of Anther.
Single Layered.
Made up of Flattened cells.
Performs the Role of Protection.
2) Endothecium : Single or multi-layered.
Radially elongated contain
Fibrous band of U- Shaped
Helps in dehiscence.
3) Middle Layer : Parenchymatous cells.
One to three layer.
Degenerate before meiosis of PMC.
Store food for PMC.

5. 4) Tapetum : Innermost layer , Single layer, Sporogenous tissue present in it
Food to the sporogenous tissue passes through it
The tapetum is of two types:
i) Amoeboid: Cell wall of tapetum breakdown early period of
development & protoplast moves to anther cavity
Protoplast form periplasmodium
On maturity, periplasmodium contribute in formation of
exine
ii) Secretary: Cell wall of tapetum breakdown after maturity of pollen
grains. Protoplast move into pollen sac.
Function of Tapetum : Nutrient transported through tapetum
Helps in callase enzyme
Helps in development of pollen grains
Formation of exine
Pollen Allergene protein get from it

6. Sporogenous Tissue
Pollen Grains Develop from Sporogeneus Tissue
Primary sporogenous Cells directly acts as MICROSPORE MOTHER CELL (MMC)
OR Divide to increase no. then act as MMC
Each MMC under goes Meiosis and form four haploid Microspore
The Process Of formation of microspore is called as MICROSPOROGENESIS

7. Microsporogenesis
The Process of Formation of Microspores is known as Microsporogenesis.
Meiosis division is essential in all sexual reproducing organisms.
In Angiosperms the MMC which are diploid undergoes meiosis and haploid pollen
grains are formed.
Meiosis takes place in two step: Meiosis I & Meiosis II
Meiosis I is actual reduction division in which two haploid cells are formed.
Meiosis II is normal mitotic division where two haploid cell divide into Four cell.

8. Meiosis
 Meiosis takes place in two steps-
Meiosis I includes the following stages
Prophase- I
Leptotene
Zygotene
Pachytene
Diplotene
Dikinesis
Metaphase - I
Anaphase – I
Telophase – I

9.  Meiosis II takes in following stages –
Prophase -II
Metaphase - II
Anaphase – II
Telophase – II

10.  Cytokinesis
The process of wall formation after meiosis division called as Cytokinesis.
It is of two types-
1) Sucessive – Cell plate formation takes place after meiosis I
2) Simultaneous – Cell Plate formation takes place after meiosis II

11. Types of Pollen Tetrads
 Arrangements of Four pollen Grains inside the Anther are called as pollen tetrads
1) Tetrahedral – The 4 pollen grains remain at the four corner of tetrahedron.
Only 3 pollen grains are visible 1 lies behind them.
2) Isobilateral - The Four pollen grains arranged in one plane.
3) Decussate – The pollen grains are opposite to each other but each pair is at the
right angle to one above and below.
4) T- Shaped – The Two pollen grains are opposite to each othe remaining two are
above one other forming T shaped structure.
5) Linear- The pollen arranged one above the other forming linear pattern.

12. Male Gametophyte
 The pollen grains is the mother cell of the male gametophyte.
 The nucleus of pollen grains divides into two cells smaller generative cell and
larger vegetative cell.

13. Structure of pollen grain
 Outer layer Exine.
 Inner layer Intine.
 Exine is composed of Sporopollenin.
 Oily layer on pollen grain is known as Pollen kit,
thick viscous layer with odour stickiness and colour.
 Intine composed of pectin and cellulose.
 The cytoplasm contains golgi, mitochondrion, E.R.
and vacuole.
 Initial pollen grain contain single nucleus which
divides into two unequal size nuclei, larger
vegetative and smaller is called generative.

14. Development of Male Gametophyte
 First division in pollen grains results in formation two unequal cells, larger
vegetative and smaller generative.
 Vegetative cell form pollen tube and generative cell form two male gametes or
sperm.
Vegetative Cell
Vegetative cell increases in size and also increase in cell organales no. & size.
It includes Ribosome, E.R., Plastids, Golgi, Mitochondria.
Nucleus is spherical or irregular in outline containing Chromosomes.
Generative Cell
Initially it attached to intine, lateron detached from pollen wall.
It lies freely in cytoplas of vegetative cell but there is no cytoplasmic connection.
It also contain Ribosome, E.R., Plastids, Golgi, Mitochondria, Microtubles.

15. Megasporangium
 Gynoecium is the female reproductive part of
flower.
 It is made up of one or many Carpel.
 Carpel made up of two parts lower Ovary and upper
part is Stigma.
 Middle filament connects ovary and stigma is known
as Style.
 Ovary includes ovules which converted into seed
after fertilization.
 Ovules in its nucellus bear embryo sac.
 Female gametes is develops into embryo sac.
 Megasporangium together with its protective
covering is called as ovule.

16. Structure of ovule
 Integuments : Outermost covering around nucellus is called as
integument. It may be unitegmic or bitegmic. When abs. known as
ategmic. Outer integument massive, thicker, and shorter than
inner Inner Integument projects beyond outer.
 Micropyle : Small pore form by integument at tip of the ovule it is
called as micropyle In bitegmic it form by Two integument then it
is known as exostome and when they form by one integument
then it is known as endostome.
 Nucellus : It is the outer wall of megasporangium. Each ovule has
only one nucellus. Made up of parenchymatous tissue. Enclosed by
integuments. It is used as nutrition by embryo sac or endosperm.
 Hypostase and epistase : Group of cells present below embryo sac
and above the vascular supply to funiculus. The modified cells of
of nucellus present at top of the embryo sac are called as epitase
 Obturator : Uni or Multicelluar hairs are present in basal part of
the ovule.

17. Types Of Ovules
 Orthotropous – Straight ovule with micropyle chalaza and
funicle lie on one line. Also called atropous.
 Anatropous – It is backwardly turned is called as anatropous.
Micropyle lie closely to the funiculus. The ovule turned
backward by an angle of 180
 Hemitropus – The ovule placed horizontally placed on the
funicle ovule placed in angle of 90 nucellus and embryo sac
present in one direction
 Amphitropus – It is similar to anatropous but embryo sac
within ovule also bend and become horse shooe shaped.
 Campylotropus – Its is same as hemitropus oveule but the
micropyle bends toward placental side. Nucellus and embryo
sac also bends downwards side. Does not in line.
 Circinotropous – It is It is orthotropus ovule in which funicle is
very long. The funicle forms complete circle around the body
of ovule

18. Megasporogensis
A single hypodermal cell in the nucellus function as archesporial initial.
It is larger dense cytoplasm and prominent nucleus.
It is present in sporogenous tissue.
Mmc undergoes in Meiosis division to form four haploid megaspore
Megaspore arranged in the form of linear tetrad.
Out of the four megaspore only one remaine fuctional , other degenerates
Nucleus of the megaspore divide and embryo sac form

19. Female Gametophyte
 Female Gametophyte also known as embryo sac
 It is seven celled and eight nucleus structureA
 A large central cell with 2 polar nuclei
 At Micropylar end there is egg apparatus consist of egg
with two synergids
 At Chalazal end two three antipodal cells present
 The cell of egg apparatus and antipodal cell are
uninucleate and haploid where as central cell is
binucleate and diploid

20. Structure of Embryo Sac
 Egg Aparatus – Present on micropylar end, three cell structure, two synergid
and one egg cell
 Synergids – Elongated cell, upper part of cell hooked, and form filiform
ammaratus at micropyler side. It play imp role in directing pollen tube growth
the generating synergid form seat for pollen tube discharge filiform apparatus
helps in absorption transportation of material into embryo sac from nucleus
 Egg – it is present in between two synergids it has common cell wall with
synergid and central cell, having a large and single prominent nucleus . Large
amount of starch and ribosome
 Antipodal cells- Three antipodal cells present at chalazal end degenerates
before or after fertilization, store food helps in nutrition, to develop embryo
and endosperm also secrete substance which control the development of
embryo sac
 Central cell – it include two nuclei present in center diploid in nature which
fused with male germ cell, also known as endosperm mother cell

21. Fertilization
 Fusion of male gamets with female gametes is called as
fertilization.
 Pollen landed on stigma and germinate on it
 Develops pollen tube toward embryo sac.
 Two Generative cell or male gametes transported toward egg in
embryo sac
 Pollen tube discharge two male gamets, vegetative nucleus, some
amount of cytoplasm
 Some pollen grains form single pollen tube, called monosiphonous
 While some produce more than one is called polysiphonous.

22. Pollen tube entry
 Porogamy – Pollen tube enter through micropyle.
 Chalazogamy – pollen tube enter through chalazal end.
 Mesogamy – pollen tube enter through integument .

23. Double Fertilization and triple fusion
 Both the male gametes released by pollen grains involvement in fertilization
called double fertilization
 One gametes fuse with egg called syngamy and form embryo or zygote
 while other gametes fuse with central polar nuclei and form endosperm
nucleus which is called as triple fusion
 It involve fusion of three nuclei.
 This endosperm is triploid.

24. Endosperm
 Nutritive tissue provide nourishment to developing embryo.
 It is developes from primary endosperm nucleus.
 The fusion of male gametes with the polar nuclei produce it.
 The endosperm in angiosperm is triploid.
Significance of endosperm
 It is important nutrient source for developing embryo.
 At the time of fertilization little source of nutrition is available in the embryo
sac so, new source of nutrition is necessary.
 The embryo do not develop if endosperm is absent.
 If endosperm is abortive complete developments of embryo do not occur
 It is rich in fats carbohydrates and protein

25. Types of endosperm
1) Nuclear type
 It is most common type of endosperm found in 56% families
 The primary endosperm cell divides without forming cell
wall.
 The nuclei remain free in the cytoplasm of endosperm
 The wall formation may takes place later stage
 Eg. Ground nut, soyabean, cocos nusifera

26. 2) Cellular endosperm
 Cellular endosperm is found in 25% families.
 The primary endosperm cell divides wall formation start from the first
division cell wall.
 First wall formation is transverse dividing embryo sac into micropylar and
chalazal chamber.
 Division in micropylar chamber is rapid and in all direction.
 While in chalazal chamber, transverse division at slow rate.
 This results in tail like chalazal part attached to the more massive tissue at
micropyler end.
 Basal two or three cell form haustorium which penetrates into nucellar tissue
to absorb nutrition.
 It is special character of cellular endosperm.

27. 3) Helobial endosperm
 Helobial endosperm is intermediate between cellular and
nuclear endosperm
 Primary endosperm nucleus moves to the chalazal end of
embryo sac
 After first division, the cell wall formation results into two
development two chamber.
 In Micropyler chamber regular cell wall formation occur and
become a multicellular
 In small chalazal chamber nuclie remain free

28. Suspended animation
 It is also called as seed dormancy
 It is the state of seeds in which seed do not germinate even after getting
favourable condition.
 Such seed call as dormant seeds and state is called a suspended animation or
dormancy.
Primary Dormancy
 When Seed Failed to germinate due to intrinsic factors of seed then it is
called as primary dormancy.
 Immaturity of embryo.
 Impermiability of seed coat to water and oxygen.
 Restrition in the embryo development due to some reason.
 Special requirement of temperature and light.

29. Secondary dormancy
 Secondary dormancy in the seed develops due to some changes occurring
during storage
 There are several reasons of seed dormancy
 Seed Coat Dormancy
 Embryo Dormancy
 Germination inhibitors