The Open Door Web Site
Part VII : Reproduction in Flowering Plants
Other Methods of Dispersal
Pea pods (fruits) showing thier seeds inside
Wood anemone in fruit
Blackberries showing the ripe fruit (black)
REPRODUCTION IN PLANTS
Fruits and Seeds
Since plants do not move from place to place, they have developed ways to make certain that their seeds are taken well away from them; this is called seed dispersal. Seed dispersal is important because if the seeds were to develop close to the parent plant, the young plants would not receive enough sunlight to grow. If plants are too close together they compete for light, water and minerals. It is much better if the seeds develop (germinate) in another area. Different plants have developed different ways to disperse their seeds. Some use animals, some use the wind and others literally explode, throwing their seeds away from them.
Dispersal Using Animals
Since animals do move from place to place they can be used to carry the seeds away from the parent plant. This can happen in two different ways.
Some carpels develop into fruits covered by many tiny hooks. The burdock and goosegrass fruits develop like this.
When the fruit is ripe it gets caught in the fur of an animal which brushes against the plant. As the animal moves along, the fruit gets more and more tangled up in its fur until it touches the skin of the animal. At this point the animal is irritated by the fruit and uses its legs or teeth to pull the fruit out of its fur. The fruit is then left on the ground and the seed can germinate well away from the parent plant.
Other carpels develop into succulent fruits, such as grapes, oranges and berries. Many animals, including birds, eat these fruits. The animal often moves away from the parent plant to eat the fruit. The animal is eventually left with the hard seed or seeds in the centre of the fruit, which it spits out. The "stone" inside a plum or a peach is really the seed which was inside the fruit. If the conditions are right, these seeds will germinate where they were left by the fruit-eating animal.
Some animals, such as birds, eat the whole fruit, including the seeds. The seeds pass straight through the digestive system of these animals unharmed. They are then eliminated with the rest of the waste. By this time the animal has moved a long way from the parent plant and the seed is surrounded by a supply of manure which will help in its development.
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