THE DISPERSAL OF FRUITS AND SEEDS
The seeds or fruits where seeds are enclosed must be dispersed a certain distance from the “mother plant” so as they can produce effective seedlings. The reason for doing this is to avoid to compete for the necessary resources such as water, nutrients or sunlight. A seedling germination near a grown- up plant is likely not to be successful.
The main dispersal agents are the following:
Fruits dispersed by wind are provided with certain adaptations to take profit of wind force. The wings of the samaras spin when the wind blows. Many plants of the daisy family have developed some feathery hairs which make them float in the air like a parachute, such as the one of the ragwort depicted above.
Animal dispersion can be mainly done in two ways:
1) The fruit gets stuck in the animal body, either in the furs, feathers or claws. By changing place the animal unintentionally transports the fruit from one place to another. Fruits or seeds of this kind usually have some sort of hook structures, like the pod of Scorpiurus vermicula, a wild bean.
2) The most common way of animal dispersion is produced by ingestion of fruits or seeds. Afterwards, they are excreted at a long distance from the initial point. Many seeds need to be ingested in order to initiate germination. This is the reason why plants produce fruits. Fruit are intended to attract animals that by eating their fleshy content disperse their seeds. This explains why fruits tend to be so conspicuous. Olive trees follow this way in collaboration with thrashes and starlings, birds that are the principal agents of dispersion of wild olive trees.
Water dispersion occurs in plants living in the water or very near to it, like in the case of coconuts that can float on water for many miles before landing in a different place from the original point.
Self- dispersion is done by plants that expel their seeds by means of explosive capsules that throw them away. This is the case of squirting-cucumbers.
More information about plant cultivation.
23 March, 2021