4.1
Aerobiology teaching from a botanical perspective
Giuseppe Frenguelli, University of Perugia, Perugia, Italy
The plants have a close relationship with the aerial environment, from which they receive carbon and energy, but which represent an indispensable way of communication and transport. Indeed, most particulate material in the atmosphere, which constitutes the basis of aerobiological studies, is made up of biological particles of plant origin, such as algae, fungal spores, moss and fern spores, pollen, minute seeds, plant fragments. These particles are released into the atmosphere, dispersed by air currents, and then deposited on a surface. The purpose of this mechanism is above all to be found in the possibility that plants have to exchange signals, messages, reproductive particles, or ensure that their own genome can spread over the widest possible territory, thus overcoming the single individual’s impossibility to move freely in the environment.
Some microalgae live on the ground or in other habitats where there is a sufficient quantity of water and from where some vegetative cells can be dispersed by the wind or turbulent movements of the air. They are found not only outside, but also indoors, in household dust, and can develop on many damp surfaces, which enable their growth.
Superior plants have adaptations, which enable the use of the atmosphere for the dispersal of reproductive structures. It is easy to find moss spores in the air, above all because they often develop on walls and roofs so that the spores are easily transported by air currents and float in the air before depositing on a substratum. Instead, it is more difficult to find ferns spores in that they are normally close to the ground, which makes it difficult for them to be suspended in the air.
When the source of the plant material released into the atmosphere is an anemophilous plant, the airborne particle will be a pollen grain which, released by the anther of a flower, will be deposited on the stigma of another flower and cross-fertilization will take place. The pollen production is a consequence of genetic factors and meteorological conditions during the development cycle of the plant and its release is characterized by a time distribution which is the consequence of the various flowering stages. The weather conditions directly influence pollination by determining the time of onset of flowering, the abundance of vegetation and by controlling the amount of pollen that is discharged into the air from day by day.
Moreover, in the spermatophyta the dispersion of fruits and seeds are sometimes guaranteed by the wind and often its action is facilitated by some adaptations such as the lightness of the dispersal element, the presence of hairs or wings which offer an increased surface to be caught up by the wind.
Thus, the life and the survival of many species is linked to the possibility that some particles can and must be transported in the atmosphere and the knowledge of the mechanisms which regulate the release, the transport and the deposit of these particles can improve the life cycle of many wild and cultivated plants.
Session 4, Aerobiology Curriculum Development
Wednesday, 16 August 2000, 1:30 PM-4:30 PM
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