Pollenatlas

species: Betula pendula (Silver Birch)
plant family: Betulaceae
at aerobiological analyses usually achieved determination level: Betula

photos: Landesagentur für Umwelt, Bozen (Italy)

description:
outline: circular in polar view, circular to elliptical in equatorial view (oblate)
size: polar axis: 22.6 (21-25) µm, equatorial axis 24.0 (22-25) µm
apertures: triporate pollen with protruding pori, seldom also tetra- or pentaporate; vestibulate
pollen wall: thin scabrate exine, annularly thickened around the pori. A thin exine forms a vestibulum underneath the porus; small oncus.

remarks to the plant:
The main European species are Silver Birch (B. pendula) and Downy or White Birch (B. pubescens). Most of the specimens are hybrids of these two species. In Arctic and High Alpine zones and in bogs, Dwarf Birch (B. nana) represents a third important species. Birch grows preferably as a pioneer on poor, acidic or wet soils wherever much light is available as for instance on river banks, wet meadows and pastures, bogs, or clear cuttings in the forests.
Flowering catkins are produced already during summer and appear next spring together with or short before leaf development. Female flowers hibernate protected by bud shields, exposing the pistils short before the male catkins open and thus favouring pollination from other individuals. The attractive male catkins are usually yellow-brown, pendant, and longer than the females, which are initially erect, becoming pendant with seed maturation. Flowering time is March to May (June) – depending on latitude and altitude.

species: Brassica napus (Rape)
plant family: Brassicaceae
at aerobiological analyses usually achieved determination level: Brassicaceae

photos: Landesagentur für Umwelt, Bozen (Italy)

description:
outline: rounded triangular in polar view, circular to elliptical in equatorial view
size: polar axis: 22.8 (21-24) µm, equatorial axis 24.0 (23-25) µm. Size can vary within cultivars, - oil seed rape pollen is usually clearly bigger.
apertures: tricolpate, colpi rounded at their end. Colpi often covered with fine granules
pollen wall: reticulate exine, with more or less constant width of meshes, scarcely becoming smaller towards the colpi (as opposed to the reticulate tricolporate Salix-species). Muri of the reticulum with lines of tiny knobbles in top view. Open lumina of the reticulum at the edge of the colpi result in blurred colpus outlines. Exine becomes somewhat thinner (with shorter columellae) towards the colpi.

remarks to the plant:
Rape is used in many cultivars as oil seed rape. Run to seed, it grows spontaneously in cultivated fields, gardens, along waysides and devastated land. Rape is 70% self-pollinating and 30% cross-pollinated. Even if wind and insects are absent, seed are still produced. It competes with alfalfa and clover for insect pollination. The plant has bald, blue frosted leaves. The golden yellow flowers have sepals that are spreading horizontally or upright. They are arranged in clusters, opened flowers may stand partly lower than the buds. Flowering time extends from late spring to fall over a time span of about three or four weeks.

species: Broussonetia papyrifera (Paper Mulberry)
plant family: Moraceae
at aerobiological analyses usually achieved determination level: Moraceae, Moraceae/Urticaceae group

photos: Landesagentur für Umwelt, Bozen (Italy)

description:
outline: circular
size: polar axis: 13.4 (11.9-14.8) µm, equatorial axis: 14.1 (12.9-14.8) µm.
apertures: diporate pollen, apertures about 1.5 µm wide. Sometimes with tiny dots in the opening (operculum ?)
pollen wall: thin, psilate or scabrate exine, thin intine, with 2-3 µm wide onci.
additional attribute: subtle granular plasma.
note: similar pollen: Morus, Urtica, Parietaria

remarks to the plant:
Paper mulberry originates from China and Japan. It is easy to grow and has been introduced to Southern Europe and parts of the USA. The species is dioecious, flowering in April and May. Male trees have pendent catkins, females stand together in globular inflorescences.

species: Buxus sempervirens (Box)
plant family: Buxaceae
at aerobiological analyses usually achieved determination level: Buxus

photos: Landesagentur für Umwelt, Bozen (Italy)

description:
outline: more or less circular or elliptical, irregular shape
size: 28.9 (25-35) µm x 32.3 (29-38) µm
apertures: perporate (pantoporate) pollen, numerous irregular, mostly elongated and blurred pori. Pori look like cracks in a broken reticulum.
pollen wall: exine about 1,5 µm thick, reticulate, intine also about 1,5 µm thick, muri of the reticulum appear dotted
additional attribute: granular plasma with leucoplasts

remarks to the plant:
Box is an evergreen, very adaptable and durable shrub or small tree, frequently planted in parks and gardens because of its small, leathery leaves, its dense growth and the fact that it can be trimmed to almost any desired form. If not curbed, the inconspicuous yellowish-green flowers appear between March and May. Several male florets with eye-catching yellow stamens surround a female floret. A lot of easily accessible nectar attracts bees.