SEXUAL REPRODUCTION IN PLANTS

1. SEXUAL REPRODUCTION IN PLANTS Types of flowers Self-pollination vs Cross-pollination Insect-pollinated vs Wind-pollinated Fertilisation

2. FLOWERS Unisexual Bisexual Flower with either the male part or the female part Flower with both the male and female parts male and female flowers can be found on same plant (Monoecious plant) male and female flowers are borne on separate trees (Dioecious plant) e.g. hibiscus, morning glory, string bean plant e.g. papaya plant (see next slide) e.g. maize plant Mrs Theresa Teo GE2003

3. papaya flowers Mrs Theresa Teo GE2003

4. maize flowers Mrs Theresa Teo GE2003

5. POLLINATION • What is pollination? • To reproduce sexually, you need to fuse a male sex cell with a female sex cell. • The male sex cell must be brought to the female sex cell. In animals, there is the mating process. • How about for plants? They can’t move from place to place! • They need an external agent and since it is the male sex cell which are contained in the pollen grains that gets transferred , the process of transferring the pollen grains from the male part of the flower to the female part is known as pollination. • Pollination must occur before fertilisation can occur. Mrs Theresa Teo GE2003

6. Pollen Mrs Theresa Teo GE2003

7. POLLINATION Flower A of Plant A Flower B of Plant B Flower B of Plant A Mrs Theresa Teo GE2003

8. SELF-POLLINATION Pollen grains falling on the stigma of the same flower or of a different flower but of the same plant Not favoured because offspring weaker and less adaptable to changes in the environment. Analogy : Marrying within same family CROSS-POLLINATION Pollen grains falling on the stigma of another flower of the same kind but on a different plant Favoured because offsprings healthier and has more variety. Self-Pollination vs Cross Pollination Mrs Theresa Teo GE2003

9. Self-pollination vs Cross-pollination Mrs Theresa Teo GE2003

10. How does a plant ensure there are more chances of cross-pollination than self-pollination? • Presence of dioecious plants • For those with bisexual flowers, the male and female parts of the flower mature at different times • The male and female parts of a bisexual flower may be some distance away or at a certain position such that self-pollination is difficult. Mrs Theresa Teo GE2003

11. Helpers of Pollination • Pollen cannot move on its own from the anther to the stigma. • Help must be given. • The insects and the wind help in transferring the pollen. • However, insects and wind are very different helpers so insect-pollinated flowers and wind-pollinated flowers must look very different from each other to facilitate the process. • How different are they? Mrs Theresa Teo GE2003

12. Insect-pollinated Flowers vs Wind-pollinated Flowers Mrs Theresa Teo GE2003

13. Insect pollinated flower e.g. Hibiscus Mrs Theresa Teo GE2003

14. wind pollination - grass flower Mrs Theresa Teo GE2003

15. Grass flower Mrs Theresa Teo GE2003

16. Wind pollination e.g. Maize, grass Mrs Theresa Teo GE2003

17. Sexual parts of a flower Mrs Theresa Teo GE2003

18. Releasing the pollens Mrs Theresa Teo GE2003

19. Mrs Theresa Teo GE2003

20. Fertilization When all the ovules have been fertilised, the petals, stamens, stigma and style are no longer needed. They will usually wither and fall away, leaving an ovary in which the ovules are developing into seeds. Mrs Theresa Teo GE2003