1. Sexual Reproduction in Flowering Plants
Part 1: Flower Structure & Gamete Formation
Video

2. Learning objectives(1/4)
State the structure & function of the floral parts including: Sepal, petal, stamen, carpel)
State that the Pollen grain produces male gamete.
State that the Embryo sac produces an egg cell & polar nuclei.

3. Structure of the flower

4. Structure of the flower

5. Structure of the flower

8. Part Function Sepal Petals Receptacle Stamen (Male Part) Carpel
To protect the flower when it is a bud
Petals
Brightly coloured to attract insects to the flower for pollination
Receptacle
Supports the flower parts
Stamen
(Male Part)
produce the pollen grains
Anther
Produces pollen
Filament
Holds the anther in place
Carpel
(female part)
To produce the ovules
Stigma
Where pollen lands after pollination
Style
Pollen travels down this
Ovary
Contains ovules

9. The Pollen grain produces male gamete.

10. The Embryo sac produces female gametes called the egg cell & polar nuclei.

12. Can you…..
State the structure & function of the floral parts including: Sepal, petal, stamen, carpel)
State that the Pollen grain produces male gamete.
State that the Embryo sac produces an egg cell & polar nuclei.

13. Sexual reproduction in the flowering plant (Higher Level)

14. Learning Objectives
Outline pollen grain development from microspore mother cells
Outline embryonic sac development

15. Pollen Grain (Microspore) development http://www. biology

16. Pollen grain development
An anther consists of 4 pollen sacs
Pollen Sac

17. Pollen grain development
Each pollen sac is surrounded by a layer of cells called tapetum (a food store that supplies energy)
Vascular bundle supplies food and water

18. Pollen Mother Cells (2n)
Fibrous Layer
Tapetum
Pollen Mother Cells (2n)
Pollen

19. Pollen Grain development
Microspore mother cells (2n) are located in the pollen sacs
They are diploid
They divide by meiosis to produce a group of four haploid cells called a tetrad
Each tetrad breaks up to form four separate haploid pollen grains

20. Pollen Grain development
Microspore mother cell (2n)
Tetrad of pollen
Meiosis
Separation
Pollen Grains (n)

22. Pollen Grain development
Pollen grains have 2 coats
Exine: outer layer
Intine: inner layer
Pollen grains divide by mitosis producing two haploid nuclei:
Tube nucleus – forms the pollen tube
Generative nucleus – form the male gametes
Tube nucleus
Mitosis
Generative nucleus

23. Pollen Grain development
When pollen grains have matured the walls of the anther dry and split
Pollen grains are then exposed and are ready for pollination

24. Pollen Grain development
After pollination the generative nucleus (n) divides by mitosis to form two sperm nuclei (n)
These will each play a role in double fertilisation

25. Pollen Grain development

26. The pollen grain produces male gametes.
The pollen grain is not the male gamete.

28. Learning Check How many pollen sacs does an anther have?
What form of cell division takes place in a pollen mother cell?
What is the group of four pollen cells called before they separate?
What form of cell division takes place to produce the generative nucleus and tube nucleus?

29. Embryo sac (Megaspore) development

30. Each ovary contains one or more ovules
An ovary has two walls called integuments
Between the integuments is a small opening (micropyle) through which a pollen tube can enter.
The nucellus provides nutrients for growth in the ovule
nucellus
Integuments
micropyle

31. Megaspore mother cell (2n)
One cell in the ovule, the megaspore mother cell (2n) divides by meiosis to form four haploid cells
Three of these cells disintegrate
The remaining cell is called the embryosac.
Meiosis
Embryo sac (n)

32. Gametes Polar nuclei (n)
The nucleus of the embryo sac (n) divides by mitosis three times forming eight haploid nuclei
These are still contained within the embryo sac
Five of these nuclei will later disintegrate
The remaining three are the gametes, two of these form the polar nuclei in the embryo sac
The remaining female gamete forms an egg cell
Gametes Polar nuclei (n)
Gamete – Egg cell
(n)

33. Megaspore mother cell (2n)
Meiosis
Embryo sac (n)
Mitosis (3 times)
Polar nuclei
Egg cell

35. Learning Check
What form of cell division takes place in a megaspore mother cell?
Are the cells formed diploid or haploid?
What happens to one of these cells?
What form of cell division takes place in the embryo sac and how many times?
How many nuclei are formed?
What is the fate of these nuclei?

36. Name the following parts
A = Stigma B = Ovary C = Embryo sac D = polar nuclei E = Ovule (integuments)

37. Can you….
Outline pollen grain development from microspore mother cells
Outline embryonic sac development
Flower