Spadix

Spadix

The spadix is ​​a particular type of inflorescence, similar to the ear, which we can find in many species of monocotyledons. The spadix is ​​present mainly in the Araceae family.
The spadix is ​​often wrapped by a colored leaf; this is a particular bract that assumes functions of recall towards the pronubi and takes the term of spata.
The spadix is ​​characterized by a main axis, which is often thickened and flowers that can be unisexual and without peduncle (sessile).
The flowers are arranged on the axis according to a precise order: fertile female flowers in the basal part, fertile male flowers in the middle part and sterile female flowers in the terminal part.

 

Being unisexual the male flowers are reduced to the stamens only and the female ones to the ovary only.
The spadix is ​​characterized by a particular type of pollination, in fact the insect, attracted by the spatula, penetrates into the sterile female flowers placed above and characterized by having the stylus turned downwards and externally covered by a series of hairs that push the insect downward. In this way it slips into the fertile female flowers and fertilizes them. Once fertilization has occurred, the insect can not leave the flower because of those same hairs that had pushed it down and remains imprisoned until the formation of male gametophytes (germinated pollen grains). At that point the male stamens begin to mature producing the pollen and at the same time the sterile flowers are atrophied. In this way the insect escapes only after the flower has secured the transport on another flower of its own pollen.
In this inflorescence the antesis, ie the period in which a flower is completely open and functional, takes place from the bottom upwards.




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