Gynoecium, Megasporogenesis, Monosporic development of Embryo, Embryo sac, Pollination types

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3. Gynoecium
• The gynoecium represents
the female reproductive
part of the flower.
• The gynoecium may
consist of a single
pistil or Carpel
(monocarpellary).

4. • The gynoecium may consist
of a single pistil
(monocarpellary).
• Example: Hibiscus

5. Gynoecium
• The gynoecium may have more than one pistil
(multicarpellary).
• Syncarpous and Apocarpous.

6. B). more than one, the
pistils may be fused
together (syncarpous)
Multicarpellary,
syncarpous pistil of
Papaver;
Papaver;

7. C). More than one, the pistils
may be free (apocarpous)
multicarpellary, Michelia;
Michelia;

8. Ovules or Megasporangium

9. • Only one ovule is present in Wheat, Paddy, Mango.
• Many ovule are present in Papaya, water melon and
orchids.

10. The Megasporangium (Ovule) :

11. The Megasporangium (Ovule) :
Funicle
Hilum Integuments
Nucellus
(2n)
Embryo sac
(n)
Micropyle
Chlaza

12. Funicle and Ovule:
• The ovule is a small structure attached to the placenta by
means of a stalk called funicle.
• The body of the ovule fuses with funicle in the region
called hilum.
• Thus, hilum represents the junction between ovule and
funicle.

13. Integuments.
• Each ovule has one or two protective envelopes called
integuments.
• Integuments encircle the nucellus except at the tip where
a small opening called the micropyle .
• Opposite the micropylar end, is the chalaza, representing
the basal part of the ovule.

14. Nucellus.
• Enclosed within the integuments is a mass of cells called
the nucellus.
• Cells of the nucellus have abundant reserve food
materials.
• Located in the nucellus is the embryo sac or female
gametophyte.
• An ovule generally has a single embryo sac formed from a
megaspore.

15. There are 6 types of ovules

16. 1.Orthotropous ovule: The body of the ovule is straight.
The funicle, hilum, chalaza and the micropyle lie in a straight line
2. Anatropous ovule (ana - backward or up, tropous - turn):
• The body of the ovule becomes completely inverted (180°) during
the development so that the micropyle lies very close to the hilum
3.Hemi-anatropous or hemitropous ovule:
The body of the ovule (90°) is placed transversely at right angles to
the funicle. The micropyle and chalaza lie in one straight line

17. • Pollenkitt is the most common adhesive
material present around pollen grains of
almost all angiosperms pollinated by animals..
• It is made up of lipids and carotenoids..

18. Megasporogenesis
• The process of formation of megaspores from the
megaspore mother cell (MMC) is called
Megasporogenesis.
• Megaspore mother cell (MMC) in the micropylar region of
the nucellus.

19. • MMC is a large cell containing dense cytoplasm and a
prominent nucleus.
• The MMC undergoes meiotic division.
• Meiosis results in the production of four megaspores..

22. Female gametophyte :
• In a majority of flowering plants, one of the megaspores
is functional while the other three degenerate.
• Only the functional megaspore develops into the female
gametophyte (embryo sac).
• This method of embryo sac formation from a single
megaspore is termed monosporic development

23. Monosporic development.
Functional
megaspore
1 mitosis
2 mitosis 3 mitosis

25. Embryo sac (Female gametophyte)
Egg
Apparatus

26. • The nucleus of the functional megaspore divides
mitotically to form two nuclei.
• Each nuclei move to the opposite poles, forming the
2-nucleate embryo sac.
2-nucleate embryo sac.

27. Two more sequential mitotic nuclear divisions:
4-nucleated embryo sac
• Formation of the 4-nucleate and later the 8-nucleate
stages of the embryo sac.
• Mitotic divisions are strictly free nuclear, that is, nuclear
divisions are not followed immediately by cell wall
formation.

28. After the 8-nucleate stage…
• After the 8-nucleate stage, cell walls are laid down
leading to formation of embryo sac.
• Six of the eight nuclei are surrounded by cell walls and
organised into cells;
• the remaining two nuclei, called polar nuclei are
situated below the egg apparatus in the large central
cell.

29. • Typical angiosperm embryo sac, at maturity, though 8-
nucleate is 7-celled.
• This type of embryo sac is called polygonum type
because it was discovered by Strasbuger in polygonum
plant.

30. • The function of the Antipodal cells is to provide
nourishment to the egg cell.
• The synergids act as a site of the discharge of the
male gametes of the pollen tube.

31. • The synergids have special cellular
thickenings at the micropylar tip called
filiform apparatus.
• Filiform apparatus play an important
role in guiding the pollen tubes into the
synergid.

32. Central cell
• The large central cell, as mentioned earlier, has two polar
nuclei.
• Six of the eight nuclei are surrounded by cell walls and
organised into cells.
• The remaining two nuclei, called polar nuclei are
situated below the egg apparatus in the large central
cell.

33. Central cell

34. Pollination

35. • Pollination: Transfer of pollen grains (shed
from the anther) to the stigma of a pistil is
termed pollination.
• Kinds of Pollination :
• 1.Autogamy
• 2. Geitonogamy
• 3.Xenogamy

36. Autogamy:
• Transfer of pollen grains from the anther to
the stigma of the same flower.
• Complete autogamy is rare

37. • Autogamy requires synchrony in pollen release
and stigma receptivity.
• The anthers and the stigma should lie close to
each other so that self-pollination can occur.
Pea plants
are naturally self-pollinating..

38. Viola (common pansy), Oxalis, and Commelina
• Chasmogamous: Flowers which are similar to
flowers of other species with exposed anthers
and stigma
• Cleistogamous: flowers which do not open at
all. In such flowers the anthers and stigma lie
close to each other.

39. Commelina
Chasmogamous
Cleistogamous
Underground
flowers

40. In Cleistogamous flowers
no chance of cross-pollen.
Pea flowers produce assured seed sets.
Pollinators not require (Pollinating agent not
require)
Advantageous: 100% seed set formation.
Disadvantageous: Offspring's produce have
limited genetic diversity.

41. • Geitonogamy: Transfer of pollen grains from the
anther to the stigma of another flower of the
same plant.
• Geitonogamy: is functionally cross-pollination
involving a pollinating agent.
• Geitonogamy: genetically it is similar to
autogamy.

42. Xenogamy
• Xenogamy: Transfer of pollen grains from
anther to the stigma of a different plant.
• Xenogamy: brings genetically different types
of pollen grains to the stigma.

43. Agents of Pollination

44. Pollination by wind

45. Dr. HarinathaReddy Aswartha
Assistant professor
Department of Microbiology
biohari14@gmail.com

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