Nectarium

Extra-floral nectaries in the cyathium of Euphorbia milii

Section through a real flower of the blue monkshood ( Aconitum napellus ). The nectar leaves are housed in the large, helmet-shaped sepal. The nectar is only accessible to long- nosed bumblebee species

A Nectary , even honey gland or nectar gland called, is a food gland in flowering plants having a sugary separates juice, the nectar .

Depending on their location, a distinction is made between floral nectaries that are inside the flower and extra- floral nectaries that are outside of the flower. According to their function, a distinction is made between nuptial nectaries, which serve to attract pollinators , and extranuptial nectaries, which do not serve to attract pollinators. Your nectar is eaten by insects, for example, which protect the plant from predators. Floral nectaries are usually also nuptial nectaries.

construction

Nectar tissue is characterized by small, plasma-rich cells . It usually consists of several cell layers and is connected to vascular bundles , but often only to the phloem .

If the epidermis is part of the nectar tissue, the nectar is released to the outside over the entire tissue surface and one speaks of an epithelial nectarium . The epidermis does not belong to the glandular tissue, the delivery of the nectar is made by Saftspalten (which the stomata homologous are), and the nectaries are mesophylläre Nektarien called.

In some plant families, such as the dipsacales , nectar is produced by single-celled hairs which together form a trichome nectarium . Multicellular hair as a nectar builder occurs in Adoxa or the mallow family .

Nectar organs

The spurred nectar organs of Aquilegia canadensis also serve to attract the pollinators

As nectar organs or nectar sheets (honey leaves) organs (reformed dust or petals), respectively, which are especially designed for nectar morphologically formation and nectar performance. They can take on different shapes: cone-shaped, funnel-shaped, tubular in Helleborus , sub-like in Trollius , flat to corolla-like in Ranunculus , as a spur , protuberance Aquilegia (bags with a spur). Or hidden in a helmet-like tepal, like Aconitum . They are either with or without a display function.

The nectar organs of the buttercup family are located between the flower envelope and the Androeceum and are often regarded as homologous to the stamens. However, this is not uncontested, they are also homologated with petals.

In the neotropical family of Marcgraviaceae there are nectar organs that look similar, but are not located in the flowers, but are located on the inflorescence axis or on the flower stalks. These are the transformed bracts of the flowers.

Floral nectaries

The nectarium in a flower can be formed in many areas of the flower. The floral nectaries are often formed as glandular surfaces (scales), bumps or hairs and in depressions (nectar, honey pits, pits, holes).

Perianth (nectar, honey leaves): In the Turkish league ( Lilium martagon ), the nectaries are located on the top of the tepals in a nectar groove (honey fold, furrow) covered with hair. In the mallow ( Malva ) they sit on the top of the sepals , in Adoxa on the top of the petals . They can also be formed as nectar and honey scales, as in buttercups ( Ranunculus ), at the base of petaloid nectar leaves that are used to display, which are located between the flowers and stamens. Sometimes the honey leaves are only small and inconspicuous, hidden between the petals or stamens, like the globe flower . They are also sometimes inconspicuous, i.e. without a display function, such as the hellebore and the monkshood . With the Adonis , the nectar production is secondarily reduced, the honey leaves are only used for viewing because the tepals are reduced. They can also lie in a spur, a hollow bulge in the area of the flower. In Delphinium , the nectaries are hidden in the protruding spur of one of the petals. A protruding nectar spur can also be formed, as in Consolida regalis or Aquilegia . The nectar spur can serve as a viewing function.

Some plants have post-floral nectaries that continue to function long after the flower has wilted. B. Attract ants to help the plants spread their seeds .

Androeceum : When crocus ( Crocus ) they sit on the outer side of the stamen base (filament or Stamennektarien), on Leingewächsen of stamens appendages. In some buttercups , all of the staminodes are converted to nectaries (staminodialnectaries).

Gynoeceum : Here septal nectaries , septum nectaries ; recessed Nektarien at the contact surfaces of adjacent carpels ( carpels be) with a duct to the outside is formed. Also, the outside of the ovary nectaries be present. Even scars can deposit nectar. Nectaries can also occur on the stylus cushion . Also on pestle lodes, reduced stamps .

Flower axis ( discus ) ( disc nectaries): Approximately as a ring-shaped, secreting elevation, thickening between Androeceum and Gynoeceum (intrastaminal disc) in the genera Calystegia , Citrus and Ruta .

Extra-floral nectaries

Extra-floral nectaries are located outside of the flowers, for example on foliage leaves. B. in the corners of leaf veins or on the leaf margin, on the rachis in pinnate leaves, on petioles (e.g. in Prunus ) or on stipules (e.g. vetch ), but they can also occur on twigs or fruits. Usually they are not related to pollination, so they are extranuptial. Exceptions are, for example, the nectaries of the euphorbias , which are located outside the strongly reduced flowers, but are part of the pseudanthias and clearly serve for pollination. The extra-floral nectaries are often used by the plants to attract insects, which protect them from predators.

Pseudonectaries

Pseudonectaries are often glittering hair or dry to moist organs and surfaces that are attractive to insects and thus attract them.

literature

Peter Leins: blossom and fruit. Morphology, history of development, phylogeny, function, ecology. E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart 2000, ISBN 3-510-65194-4 , pp. 117–128.
Veit M. Dörken: Ranunculaceae - Hahnenfußgewächse (Ranunculales) (PDF), on cms.uni-konstanz.de, accessed on February 8, 2018.

Web links

Wiktionary: Nektarium - explanations of meanings, word origins, synonyms, translations

Commons : Nectaries - collection of images, videos and audio files

Individual evidence

↑ ^a ^b ^c Gerhard Wagenitz : Dictionary of Botany. The terms in their historical context. 2nd, expanded edition. Spectrum Akademischer Verlag, Heidelberg / Berlin 2003, ISBN 3-8274-1398-2 , p. 214 f.
↑ Peter Leins: pp. 117–128.
↑ Peter Leins: p. 126.
^ SW Nicolson, M. Nepi, E. Pacini: Nectaries and Nectar. Springer, 2007, ISBN 978-1-4020-5936-0 , pp. 32-43.
↑ Pat Willmer: Pollination and Floral Ecology. Princeton University Press, 2011, ISBN 978-0-691-12861-0 , pp. 528 f.

[Wagenitz-1] Gerhard Wagenitz : Dictionary of Botany. The terms in their historical context. 2nd, expanded edition. Spectrum Akademischer Verlag, Heidelberg / Berlin 2003, ISBN 3-8274-1398-2 , p. 214 f.

[2] Peter Leins: pp. 117–128.

[3] Peter Leins: p. 126.

[4] SW Nicolson, M. Nepi, E. Pacini: Nectaries and Nectar. Springer, 2007, ISBN 978-1-4020-5936-0 , pp. 32-43.

[5] Pat Willmer: Pollination and Floral Ecology. Princeton University Press, 2011, ISBN 978-0-691-12861-0 , pp. 528 f.