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PRACTICAL 8: PLANT REPRODUCTION – POLLINATION AND SEED DISPERSAL Objective: 1. To observe plants and classify their flowers according to the type of pollinating agents 2. To observe and gather information about plants with fruits and seeds adapted for different type of dispersal Introduction: Pollination is the process by which pollen is transferred in plants, thereby enabling fertilization and sexual reproduction. Seed dispersal is the movement or transport of seeds away from the parent plant. Literature reviews: Plants have limited mobility and consequently rely upon a variety of dispersal vectors to transport their propagules, including both abiotic and biotic vectors. Seeds can be dispersed away from the parent plant individually or collectively, as well as dispersed in both space and time. The patterns of seed dispersal are determined in large part by the dispersal mechanism and this has important implications for the demographic and genetic structure of plant populations, as well as migration patterns and species interactions. There are five main modes of seed dispersal: gravity, wind, ballistic, water and by animals. Some plants are serotinous and only disperse their seeds in response to an environmental stimulus. Material and apparatus: A bag to carry note paper, pens, pencils, ruler, camera and if desires some food and drink. Plastic bags to hold flowers, fruits and seeds for later study on campus.

Practical 8: PLANT REPRODUCTION – POLLINATION AND SEED DISPERSAL

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Page 1: Practical 8: PLANT REPRODUCTION – POLLINATION AND SEED DISPERSAL

PRACTICAL 8: PLANT REPRODUCTION – POLLINATION AND SEED DISPERSAL

Objective:

1. To observe plants and classify their flowers according to the type of pollinating agents

2. To observe and gather information about plants with fruits and seeds adapted for different type of dispersal

Introduction: Pollination is the process by which pollen is transferred in plants, thereby enabling fertilization and sexual reproduction. Seed dispersal is the movement or transport of seeds away from the parent plant.

Literature reviews: Plants have limited mobility and consequently rely upon a variety of dispersal vectors to transport their propagules, including both abiotic and biotic vectors. Seeds can be dispersed away from the parent plant individually or collectively, as well as dispersed in both space and time. The patterns of seed dispersal are determined in large part by the dispersal mechanism and this has important implications for the demographic and genetic structure of plant populations, as well as migration patterns and species interactions. There are five main modes of seed dispersal: gravity, wind, ballistic, water and by animals. Some plants are serotinous and only disperse their seeds in response to an environmental stimulus.

Material and apparatus:

A bag to carry note paper, pens, pencils, ruler, camera and if desires some food and drink. Plastic bags to hold flowers, fruits and seeds for later study on campus.

Procedure:Work with your partner

1. A few of my classmates are got together and a trip to a botanical garden / around the campus is made.

2. A collection of pictures on fruits and flowers is made after observing.3. The pictures are named and the flowers are grouped according to the type of

pollinating agents they are adapted to.4. The characteristics of fruits and seeds is classified based on the types of

adaption for dispersal5. My collection is displayed in the class.

Marks will be allocated for:

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the pictures / actual fruits and seeds presented / allocated. All photographs should be numbered and have a clear title and brief description / explanation

effort put into the collection short description / written explanation given about the collection presentation quality creativity

Note that only one display collection is required for each pair of students. Both students should be listed as authors of the final display and should contribute to its preparation. The same mark will be given to each partner.

Result:

Methods of seed

dispersal

Characteristics Example Diagram

Wind Seeds with stiff wings covering the seed, have long, feathery tails, flimsy, the seed is attached to fine hairs which open out when the seed is shed to form a ball.

Hornbeam

Sycamore

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Ash

Dandelion

Williow herb

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Lalang

Water The fruits of most water plants have buoyant, waterproof coverings that allow them to float and disperse their seeds by water.

Coconut

Yellow-eyed cerbera, pong-pong tree

Lotus

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Mangrove

By splitting suddenly – Explosive action of fruit

Some fruits scatter their seeds by literally exploding. The pod dries, bursts open and forcibly shoots the seeds for several feet in all directions.

Flame of the forest

Jewelweed balsam

Lady’s finger , okra

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Red bead tree, saga

Rubber

Kapok tree

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Animals / Humans

Animals often serve as seed carriers. Seeds (with sticky hairs, bristles, hooks, or barbs) are transported by sticking to the fur of animals or on the clothing of human beings.

Birds and other animals eat the fleshy fruits and discard the seeds or they may eat both but the seeds are not digested and are passed out with their droppings, often far away from the parent plant.

Papaya

Tomato

Rambutan

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Mimosa pudica

Cherry

Water guava

Chilli

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Discussion:

Seed dispersal by water

1. The fruits of most water plants have buoyant, waterproof coverings that allow them to float and disperse their seeds by water.

2. Plants which grow beside water often rely on water to transport their seeds for them. They may produce light seeds which float, or there may be fluff that helps buoyancy. Two tall trees, Willow and Silver Birch, are often found in the middle of moorland, far from any other trees, but along the course of a stream. They can colonise such isolated places because they both have very small, light seeds, which can be carried by the wind or by water. Foxgloves and Harebells often grow beside streams. They both have light seed that floats.

3. Trees found on tropical beaches often have their seeds carried there by the sea. They have woody, waterproof coverings which enable them to float in the salty water for long periods. Coconuts are well-known travellers, as is the famous Coco-de-mer, found only on the Seychelles, but familiar before its origin was known from the giant seeds washed up on other tropical beaches.

4. Mangroves are another familiar tree of tropical beaches. Their seeds are

unusual in that they can begin germination while still on the parent plant, and they drop into the ocean when about a foot long. These 'sticks' float upright in the sea, waiting to be flung onto the beach to continue germinating.

5. Seeds of some tropical trees can even be carried along by ocean currents to land on shores half a world away. Sometimes Sea Beans, the seeds of Entada gigas, are carried from their homes beside rivers in Africa, Australia or South America, across the ocean to land on European shores.

Seed dispersal by wind

1. Some seeds are enclosed in wing-like husks (with one or two propeller blades) or fluffy coverings that help them drift some distance away from the parent plant.

2. Some tall trees produce seeds with stiff wings covering the seed that enable them to fly long distances. The wings are twisted and balanced so that the seed spins around as it is carried along by the wind. These natural

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adaptations for using the wind to transport the weight of the seed must be technically accurate, as the wings of modern planes and helicopters are designed in the same way.

3. These wings usually support one seed each, but may start off as a two-winged pod that later splits in two to release the seeds. Some seeds have only one wing (e.g. Lime or Ash). This type of attachment is quite heavy, and this system only works well in a good wind, and from a tall tree.

4. Sometimes seeds have thin wings as an extension of the seed that enable them to glide in the wind. They don't need so much wind as the seeds that fly, but they are not so heavy. The largest of this type of seed is 6" across, from a climber called Alsomitra growing in the tropical forests of Asia.

5. Some seeds have long, feathery tails which help them to fly, like the tail of a

kite.

6. Seeds that have almost weightless additions that enable them to be carried long distances by the slightest breeze are familiar all over the world.

7. These are more flimsy additions to seeds which help them to be transported long distances by the wind. These additional features are usually various sorts of fluff which are almost weightless but increase the volume of the seed, so that it can be picked up by the slightest breeze and carried over long distances.

8. Sometimes, the seed is attached to fine hairs which open out when the seed is shed to form a ball. Thistles produce seeds with this type of fluff, and thistledown is often seen blowing across motorways on its journey to colonise new sites. Many members of the Daisy family provide their seeds with a flat disk of fine hairs to produce a parachute to keep the seed aloft. Bulrushes produce many millions of dust-like seeds, each of which has its own tuft of fluff to give it a bigger area to be caught by the wind.

Seed dispersal by splitting suddenly

1. Some fruits scatter their seeds by literally exploding. The pod dries, bursts open and forcibly shoots the seeds for several feet in all directions.

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Seed dispersal by human /animal

2. Animals often serve as seed carriers. Seeds (with sticky hairs, bristles, hooks, or barbs) are transported by sticking to the fur of animals or on the clothing of human beings.

3. Birds and other animals eat the fleshy fruits and discard the seeds or they may eat both but the seeds are not digested and are passed out with their droppings, often far away from the parent plant.

4. As well as eating them, some animals collect the fruits or seeds and bury them to eat later, but forget about them and the seeds germinate in their new location. Sometimes, as in the case of Mistletoe, the seeds are covered in a sticky slime which the birds rub off on a new tree. Even humans carry seeds far away for plants - by taking an apple on a picnic, for example, and throwing the core, with its seeds, into the bushes.

5. Many plants produce fruits or individual seeds covered in hooks or spines which attach the seed to the animals's fur or feathers - or, in the case of humans, to our clothes or bags. The seeds are then carried a sufficient distance from the parent plant to give them space to grow. Eventually, the seed may fall off, or be rubbed off by the animal.

Conclusion:

All seeds have their own characteristics for their method of dispersed.

References

Dispersal of seed by animal. (n.d.). Retrieved April 8, 2010, from

http://theseedsite.co.uk/sdanimal.html

Dispersal of seed by water. (n.d.). Retrieved April 8, 2010, from

http://theseedsite.co.uk/sdwater.html

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Dispersal of seed by wind. (n.d.). Retrieved April 8, 2010, from

http://theseedsite.co.uk/sdwind.html

Explotion. (n.d.). Retrieved April 9, 2010, from

http://www.zephyrus.co.uk/explosions.html

Fire dispersal. (n.d.). Retrieved April 9, 2010, from

http://www.zephyrus.co.uk/firedispersal.html

How seeds are dispersed? (n.d.). Retrieved April 10, 2010, from

http://www.vtaide.com/png/seed-dispersion.htm

Seed Dispersal . (n.d.). Retrieved April 8, 2010, from

http://theseedsite.co.uk/dispersal.html

Seed Dispersal 1. (n.d.). Retrieved April 9, 2010, from

http://www.zephyrus.co.uk/seeddispersal1.html

Seed dispersal by animal. (n.d.). Retrieved April 8, 2010, from

http://theseedsite.co.uk/sdanimal.html

Seed dispersal by force. (n.d.). Retrieved April 8 , 2010, from

http://theseedsite.co.uk/sdforce.html