SEXUAL REPRODUCTION IN PLANTS

1. SEXUAL REPRODUCTION IN PLANTS Lesson 3: Flowers to Fruits Fruits and Seeds Dispersal of Seeds Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

2. Revision of Previous Lesson • We have discussed in great detail : pollination and fertilisation in plants. • Let’s move on to the next stage where the fertilised flowers become fruits. Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

3. From Flower to Fruit • When all the ovules in a flower have been fertilized, the petals, stamens, stigma and style are no longer needed. • They will usually wither and fall, leaving an ovary in which the ovules are developing into seeds. • The fruit protects the seeds. • What is so important about seeds such that they need protection? Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

4. Flower to Fruit Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

5. Pea fruit from flowers Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

6. The Fruit and the Seeds • Seeds will grow into new plants and ensure the continual existence of that type of plant. • However, seeds cannot grow too close to their parent plant. Why? • OVERCROWDING • Overcrowding leads to competition for: • Water • Space • Nutrients • Light • Get to grow in new habitats where conditions may be even better. Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

7. The Fruit and the Seeds • Therefore, the seeds need to be dispersed far away from their parent plant. • In what ways can seeds be dispersed? • By water, wind, animals and explosive action Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

8. Before we look at dispersal… • Take note of the THREE points: • Dispersal method of the fruit and the dispersal agent. • Characteristics of the fruit that supports dispersal. • Dispersal pattern of the fruit. Mrs Theresa Teo GE2003

9. AGENTS OF DISPERSAL • Seeds and fruits are modified in different ways to be dispersed using one or two of the agents of dispersal. • Which parts get modified? The testa and pericarp are often modified to help in dispersal Seed An ovule which has been fertilised and become mature. Its wall is the testa. A mature ovary which contains fertilised seeds. Its wall is the pericarp Fruit Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

10. Dispersal by Wind • Plants which depend on the wind for the dispersal of seeds usually have • light seeds or • wings or • a parachute of fine hairs or • feathery hairs that act like many little parachutes • to help keep them floating in the air Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

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12. Visit this website for more information on seed dispersal: http://www.vtaide.com/png/seed-dispersion.htm Mrs Theresa Teo GE2003

13. Dispersal by Water • Plants which depend on the water for the dispersal of seeds usually have • Some feature that will allow it to float • Some protective covering to protect it during its long water journey. Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

14. Pong Pong Coconut Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

15. Nipah Fruit Lotus Fruit Pod Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

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17. Dispersal by Animals • Three ways • First way • The seeds or fruits have hooks or sticky hair that catch onto the fur of animals or clothing of human beings • Second way • Fruits get eaten by animals and seeds are thrown onto the ground as they are too big to be eaten by animals; or • Fruits and seeds get eaten by animals but the seeds are too hard to be digested by animals and are passed out in the droppings • Third way • Animals collect the fruits and seeds and take them to their burrows. Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

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21. Dispersal by Explosive Mechanism or Splitting of the Fruit The fruit wall suddenly breaks into several parts and the movement causes the seeds to be shot out. This is caused by the unequal drying up of the fruit wall. The wall may split in one, two or many places along the line/lines of dehiscence (lines of splitting). Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

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23. Unripe Ripe Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

24. Ripe and unripe Kapok fruits Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

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