The dispersion - Orto botanico 'Pellegrini - Ansaldi'

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The dispersion of the fruits and seeds

Appetible fruits for birds
The whitebeam (Sorbus aria (L.) Crantz)
For the life of plants is important that after the production of fruits the seeds contained in them can be dispersed in the environment in larger and larger areas: this occurs in different ways. Seeds can be dispersed, if they are produced in a fruit that opens when ripe (dehiscent), like legumes and silique, or the fruits themselves can be dispersed, if they are indehiscent, that is if they don’t open when ripe, like it happens for caryopsis, samaras, drupes and pomes. The whitebeam and other species of the same category produce fruits that are ingested by birds, that use the pulp, attracted by the colour and by the nutritional value.
Often the seeds that pass through the digestive tract of a bird duplicate more easily and also at a striking distance from the plant that produced them; this phenomenon is called endozoocoria.

Fruits carried by animals
Common agrimony (Agrimonia eupatoria L.)
Some plants produce fruits or seeds that have on the surface particular formations like thorns, hairs or hooks. Courtesy of this adaptation, the fruits or the seeds easily attach to the fur of some animals, which carry them by disseminating them in environments more or less far from the plant that ripen them (epizoocoria).

Appetible fruits for animals
The yew (Taxus baccata L.)
The yew, or tree of death, is a very poisonous plant in all its parts, including the seed; it produces a particular fleshy structure called aril that is still eaten by animals without consequences, since they use only the external sweetish part, while the seed, covered by a resistant integument, go through the digestive tract of the animal remaining intact.

Fruits carried by wind
The common dandelion (Taraxacum officinale Weber)
The common dandelion is a very common plant species; it produces showy yellow flower heads that after pollination turn into particular infructescences, the well-known dandelions. The dandelion is made of several little fruits (achenio), placed to form a sort of sphere, each one prolonged in a light and feathery structure, with the function of a very little propeller, capable of keeping suspended the fruit letting it be transported by air flows; this type of dissemination is called anemochorous.

Fruits and seeds carried by wind I
The sycamore (Acer pseudoplatanus L.)
The mechanisms and ways with which the seeds facilitate the dispersion by wind are many, and they are based nearly always on the increase of the relationship between surface and volume. This occurs when fruits or seeds develop feathery structures, or wing-shaped structures.
The manna ash’s fruits, called samaras, are prolonged from one side in a wing; those of the sycamore have a double wing and are called disamaras. Courtesy of these structures, the fruits can easily be carried by wind.

Fruits and seeds carried by wind II
The mountain aven (Dryas octopetala L.)
The mountain aven is a glacial relict that is found in the highest parts of the Apuane. From its showy white flowers with eight petals ripe several little fruits (achenio), each one that has a feathery long filament, with the function of facilitate the dispersion.
Also in this case, with the fruits of the mountain aven that are indehiscents, that is that they don’t open when ripe, the structures suitable for the facilitation of the dispersion are not specific of the seed but of the fruit.
L'ORTO BOTANICO PIETRO PELLEGRINI, Un giardino alpino nel Parco Regionale delle Alpi Apuane
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