Reproduction in flowering plants

1. Reproduction in flowering plants Angiosperms

2. Reproduction in angiosperms • The gametophytes of flowering plants only consist of a few cells and are totally dependent on the sporophyte.

3. Reproduction in angiosperms • The gametophytes of flowering plants only consist of a few cells and are totally dependent on the sporophyte. • The development of the sporophyte generation has resulted in the huge diversity of angiosperms we see today.

4. Reproduction in angiosperms • The gametophytes of flowering plants only consist of a few cells and are totally dependent on the sporophyte. • The development of the sporophyte generation has resulted in the huge diversity of angiosperms we see today. • No external water is required for fertilisation – angiosperms have been able to colonise all terrestrial habitats.

5. Flowers • A flower is the organ of sexual reproduction in angiosperms.

6. Flowers • A flower is the organ of sexual reproduction in angiosperms. • Most flowers are hermaphrodite (both parts) but some flowers (such as kiwifruit) are unisexual (having only male or females parts on one flower).

7. Flowers • A flower is the organ of sexual reproduction in angiosperms. • Most flowers are hermaphrodite (both parts) but some flowers (such as kiwifruit) are unisexual (having only male or females parts on one flower). • Sepals protect the flower inside the flower bud.

8. Flowers • A flower is the organ of sexual reproduction in angiosperms. • Most flowers are hermaphrodite (both parts) but some flowers (such as kiwifruit) are unisexual (having only male or females parts on one flower). • Sepals protect the flower inside the flower bud. • The male part – the stamens, consists of filaments which hold up anthers which produce pollen.

9. Flowers • A flower is the organ of sexual reproduction in angiosperms. • Most flowers are hermaphrodite (both parts) but some flowers (such as kiwifruit) are unisexual (having only male or females parts on one flower). • Sepals protect the flower inside the flower bud. • The male part – the stamens, consists of filaments which hold up anthers which produce pollen. • The female parts of the flower – pistils, consist of an ovary which protects the eggs or ovules, a style, and a stigma which is often sticky to trap pollen during pollination

10. POllination • Transfer of pollen from an anther to a stigma

11. POllination • Transfer of pollen from an anther to a stigma • Self-pollination = transfer of pollen within the same flower or between flowers of the same plant.

12. POllination • Transfer of pollen from an anther to a stigma • Self-pollination = transfer of pollen within the same flower or between flowers of the same plant. • Cross-pollination = transfer of pollen between flowers on different plants of the same species. This produces greater genetic diversity. • Can be done by wind, insects, water, and birds

13. POllination • Transfer of pollen from an anther to a stigma • Self-pollination = transfer of pollen within the same flower or between flowers of the same plant. • Cross-pollination = transfer of pollen between flowers on different plants of the same species. This produces greater genetic diversity. • Can be done by wind, insects, water, and birds • Wind-pollinated plants usually have inconspicuous flowers (eg. Grasses). Pollen is produced in vast quantities as most pollens will not land on the stigma of another flower of the same species.

14. POllination • Transfer of pollen from an anther to a stigma • Self-pollination = transfer of pollen within the same flower or between flowers of the same plant. • Cross-pollination = transfer of pollen between flowers on different plants of the same species. This produces greater genetic diversity. • Can be done by wind, insects, water, and birds • Wind-pollinated plants usually have inconspicuous flowers (eg. Grasses). Pollen is produced in vast quantities as most pollens will not land on the stigma of another flower of the same species. • Insect-pollinated plants usually have large colourful flowers. Nectaries provide the nectar which attracts the insects. As insects crawl in to get the nectar, they also pick up pollen.

15. The male gametophyte • Inside a pollen grain, there are two haploid nuclei – a tube nucleus, and a generative nucleus.

16. The male gametophyte • Inside a pollen grain, there are two haploid nuclei – a tube nucleus, and a generative nucleus. • When a pollen grain germinates, the generative nucleus divides into two sperm cells and the tube nucleus forms a pollen tube.

17. The male gametophyte • Inside a pollen grain, there are two haploid nuclei – a tube nucleus, and a generative nucleus. • When a pollen grain germinates, the generative nucleus divides into two sperm cells and the tube nucleus forms a pollen tube. • Once the pollen grain has germinated, the gametophyte is mature. • Generative Nucleus – nucleus produced within a pollen grain that divides into two sperm cells.

18. The female gametophyte • Forms inside the ovules. Ovules are protected by the ovary, which forms the base of the female parts of a flower.

19. The female gametophyte • Forms inside the ovules. Ovules are protected by the ovary, which forms the base of the female parts of a flower. • Inside each ovule, specialised cells divide by meiosis to form four haploid cells.

20. The female gametophyte • Forms inside the ovules. Ovules are protected by the ovary, which forms the base of the female parts of a flower. • Inside each ovule, specialised cells divide by meiosis to form four haploid cells. • Only one of these haploid cells survive, dividing by mitosis to form 8 cells – an egg cell, an endosperm (nutrition inside the seed) mother cell and six other cells, all of which represent the female gametophyte.

21. Fertilisation • After a pollen grain has landed on a stigma and germinated, the pollen tube grows down through the style to the ovary.

22. Fertilisation • After a pollen grain has landed on a stigma and germinated, the pollen tube grows down through the style to the ovary. • One sperm from the pollen tube fuses with the egg cell to form a zygote which develops into an embryo.

23. Fertilisation • After a pollen grain has landed on a stigma and germinated, the pollen tube grows down through the style to the ovary. • One sperm from the pollen tube fuses with the egg cell to form a zygote which develops into an embryo. • The remaining sperm cell fuses with the endosperm mother cell to form endosperms (endosperms and embryo form the seed)

24. Fertilisation • After a pollen grain has landed on a stigma and germinated, the pollen tube grows down through the style to the ovary. • One sperm from the pollen tube fuses with the egg cell to form a zygote which develops into an embryo. • The remaining sperm cell fuses with the endosperm mother cell to form endosperms (endosperms and embryo form the seed) • After fertilisation the ovary forms into a fruit.

25. Seed dispersal • Succulent (or juicy fruits, such as berries and stonefruit) are eaten by animals, the seeds pass through the gut and are deposited complete with a rich supply of fertiliser.

26. Seed dispersal • Succulent (or juicy fruits, such as berries and stonefruit) are eaten by animals, the seeds pass through the gut and are deposited complete with a rich supply of fertiliser. • Many fruits become hard, tough and dry. In gorse and lupins, the dry fruit split open violently, ejecting the seeds up to several hundred metres from the parent plant.

27. Seed dispersal • Succulent (or juicy fruits, such as berries and stonefruit) are eaten by animals, the seeds pass through the gut and are deposited complete with a rich supply of fertiliser. • Many fruits become hard, tough and dry. In gorse and lupins, the dry fruit split open violently, ejecting the seeds up to several hundred metres from the parent plant. • Other seedsbecome dry and are dispersed by the wind (Dandelion)

28. Seed dispersal • Succulent (or juicy fruits, such as berries and stonefruit) are eaten by animals, the seeds pass through the gut and are deposited complete with a rich supply of fertiliser. • Many fruits become hard, tough and dry. In gorse and lupins, the dry fruit split open violently, ejecting the seeds up to several hundred metres from the parent plant. • Other seeds become dry and are dispersed by the wind (Dandelion) • By water, and by hooking onto animal fur

29. Germination • Must require • Moisture to mobilise enzymes and increase the metabolic rate of seed cells

30. Germination • Must require • Moisture to mobilise enzymes and increase the metabolic rate of seed cells • Oxygen for respiration

31. Germination • Must require • Moisture to mobilise enzymes and increase the metabolic rate of seed cells • Oxygen for respiration • Warmth to increase cell metabolic rates

32. Germination • Must require • Moisture to mobilise enzymes and increase the metabolic rate of seed cells • Oxygen for respiration • Warmth to increase cell metabolic rates • Some seeds become dormant (inactive) even when supplied with moisture, oxygen, and warmth. Dormancy in these seeds is overcome in various ways – by exposure to light, cold temperatures, or even fire.