Anemophilia

The forearms are shaken by the wind in the plain inflorescence (Medium plant)

In botany, anemophilia refers to the adaptation of many spermatophyte plants that ensure their pollination by means of the wind. The term is also applied to any dispersal of spores by wind, as occurs in many fungi or ferns.

Anemophilous species

Inflorescence of Dactylis glomerata (oil duck, poaceae). Anemophilia is typical of the grams.

Anemophily is characteristic of species that constitute dense populations in monospecific or specific pauci plant formations (with one or few species), where they are the dominant species in the ecosystem. Only then can pollination by wind be effective. Plants that grow dispersed, lost among the feet of other species, are usually pollinated by insects or other animals, that is, zoophiles, because they need specialized vectors capable of successively finding the few individuals existing in a given area. The anemophilous species, on the other hand, have to produce very large amounts of pollen, which is sometimes very noticeable in pine forests, when the soil turns yellow due to the large amount of pollen that these species produce during flowering. Only when these two conditions are met can pollination be assured.

Among the trees, the anemophilous condition is typical of conifers, which tend to form monospecific forests in cold latitudes and mountains, or of dominant trees in temperate latitudes, such as oaks or beeches. Anemophily is not found in trees in species-rich forests typical of tropical regions. Anemophilia is also characteristic of grasses and other nearby plants (such as sedges) that constitute open herbaceous formations, where the wind finds no obstacles.

Another group with anemophilous pollination is the Juglandaceae family, made up of the genera Juglans, which groups the species of walnut, Carya and Pterocarya.
In South America, the Nothofagaceae family that forms dense forests, are pollinated by the wind. Examples are Lenga, Coigüe and Ñire. One of the best known examples is the Cannabis sativa plant, this plant has small flowers which are pollinated by wind breezes.

Flower Abiotic Syndrome

Grain of pine pollen (Pinus sylvestris) showing the two side air bags that allows you to float better in the wind.

Anemophilia involves a large number of adaptations at the level of inflorescences, flowers and gametophytes. Thus, anemophilous species usually present inconspicuous flowers, without attractive petals or, directly, without any petals, as in ash trees. This disappearance of the perianth also applies to other quite typical structures such as nectaries, osmophores and nectar guides, which become unnecessary in these species. In addition, the flowers are arranged in frequently pendulous inflorescences (as for example in the pendulous male catkins of Corylus, Alnus and Quercus).

Likewise, deciduous anemophilous species tend to flower early, before the foliage appears, so that the foliage does not hinder the circulation of pollen (for example, in oaks, alders, ash trees, willows, poplars, and elms).

This particular mode of pollination requires that the pollen be small or have a very large surface/volume ratio, which reduces its sedimentation speed and makes it easier for it to travel farther when it is blown by the wind. Thus, for example, the composites of the genus Artemisia have small, smooth and dry pollen, while most of the members of the family have it larger, ornate and covered in oils, which makes it easier to agglutination and adherence to animal vectors. In pine trees, lightness is achieved by means of two hollow air sacs, which reduces their density and increases the friction surface. Likewise, the pollen grains of the anemophilous species lack pollen cement, are dry and frequently have a smooth exine, which is why they are easily separated from each other.

The production of large amounts of pollen in these species is achieved through the increase in the number of male flowers or stamens (for example, in Corylus, 2 and a half million grains are produced of pollen per stamen). The expulsion of pollen is facilitated by the mobility of the filaments of the stamens (poaceae) or by tension mechanisms of the anthers within the floral bud that literally determine the "explosion" of the flower and the concomitant release of a cloud of pollen at the time of anthesis (Urtica, Pilea).

Flowers in Beforeis Holcus mollis, look at the feathery stigmas adapted to "throw" the pollen grains that are suspended in the air, and the pendulum stamens, easily moved by the wind.

The styles and stigmas of anemophilous species are greatly enlarged in order to facilitate the capture of pollen that is transported in the air. The number of ovules in the carpels, on the contrary, is usually very low in relation to the fact that pollination is usually carried out by isolated pollen grains.