Seed Dispersal

Reproduction in plants — getting the flowers pollinated Plants have adaptations to help them in pollination. Flowers that are pollinated by animals are usually large and colourful. They also have nectar and a fragrance so that the animals are attracted to them. flower pollinated by animals

Reproduction in plants — getting the flowers pollinated Plants have adaptations to help them in pollination. Flowers that are pollinated by wind are usually small, plain and without fragrance because they do not need to attract animals. flower pollinated by wind

RECAP: 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 GE2009

Flower to Fruit Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GE2009

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

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

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 Edited Mr Lin Lixun GEO2009

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. Fruit: A mature ovary which contains fertilised seeds. Its wall is the pericarp Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

Reproduction in plants — getting the seeds dispersed Flowering plants have different adaptations to enable their seeds to be dispersed as far away as possible. The different methods of seed dispersal are… by wind by animals by water by splitting open forcefully

Reproduction in plants — getting the seeds dispersed What are the adaptations that help these fruits/seeds to be dispersed? Dispersal by wind small light dry wing-like shorea angsana

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

Dispersal Pattern - Wind Parent Wind direction Legend Offspring

Reproduction in plants — getting the seeds dispersed What are the adaptations that help these fruits/seeds to be dispersed? Dispersal by animals (eaten) bright colours sweet juicy Dispersal by animals (carried) small hooks stiff hairs How about lovegrass? How does it disperse? tomato

Dispersal by Animals Three ways First way Second way Third 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

Dispersal Pattern - Animals Parent Wind direction Legend Offspring

Reproduction in plants ― getting the seeds dispersed What are the adaptations that help these fruits/seeds to be dispersed? Dispersal by water buoyant waterproof air spaces Dispersal by splitting open dry and hard fruit wall coconut saga

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

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

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

Dispersal Pattern - Water Parent Downstream Wind direction Legend Offspring

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

Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

Unripe Ripe Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

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

Mrs Theresa Teo GE2003 Edited Mr Lin Lixun GEO2009

Dispersal Pattern – Splitting Action or Explosive Mechanism Only Parent Wind direction Legend Offspring

Dispersal Pattern – Splitting Action WITH Wind Parent Wind direction Legend Offspring

Adaptations for reproduction At a glance… Adaptations for reproduction plants seed dispersal by wind by water by animals by splitting open Fruits/seeds small light dry wing-like Fruits/seeds buoyant waterproof air spaces Fruits/seeds brightly coloured sweet juicy Fruits/seeds dry and hard fruit wall Fruits/seeds small hooks stiff hairs