Rostellum

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Cutaway drawing of Orchis mascula showing the rostellum projecting forward from the column to form cups which keep the adhesive balls sticky. Fertilisation of Orchids figure 1X.jpg
Cutaway drawing of Orchis mascula showing the rostellum projecting forward from the column to form cups which keep the adhesive balls sticky.

The rostellum is a projecting part of the column in Orchidaceae flowers, and separates the male androecium from the female gynoecium, commonly preventing self-fertilisation. [1] In many orchids, such as Orchis mascula , the pollinia or pollen masses, are connected by stipes down to adhesive discs attached to the rostellum which forms cups keeping the discs or balls sticky. [2]

Column (botany) reproductive structure that can be found in several plant families

The column, or technically the gynostemium, is a reproductive structure that can be found in several plant families: Aristolochiaceae, Orchidaceae, and Stylidiaceae.

Orchidaceae family of plants

The Orchidaceae are a diverse and widespread family of flowering plants, with blooms that are often colourful and fragrant, commonly known as the orchid family.

Gynoecium collective term for all carpels in a flower

Gynoecium is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower, it consists of pistils and is typically surrounded by the pollen-producing reproductive organs, the stamens, collectively called the androecium. The gynoecium is often referred to as the "female" portion of the flower, although rather than directly producing female gametes, the gynoecium produces megaspores, each of which develops into a female gametophyte which then produces egg cells.

In the Catasetum flower an extension of the rostellum forms a narrow feeler or "antenna" projecting forward over the labellum. Fertilisation of Orchids figure 28.jpg
In the Catasetum flower an extension of the rostellum forms a narrow feeler or "antenna" projecting forward over the labellum.

In Catasetum flowers the rostellum projects forward at each side as an "antenna", and the pollen masses are connected by a bent stalk or pedicel to a sticky disc kept moist at the back of the flower. When an insect touches an "antenna", this releases the bent pedicel which springs straight and fires the pollinium, sticky disc first, at the insect. Charles Darwin described in Fertilisation of Orchids how he "touched the antennæ of C. callosum whilst holding the flower at about a yard's distance from the window, and the pollinium hit the pane of glass, and adhered to the smooth vertical surface by its adhesive disc." [3]

<i>Catasetum</i> genus of plants

Catasetum, abbreviated as Ctsm in horticultural trade, is a genus of showy epiphytic Orchids, family Orchidaceae, subfamily Epidendroideae, tribe Cymbidieae, subtribe Catasetinae, with 166 species, many of which are highly prized in horticulture.

Pedicel (botany)

A pedicel is a stem that attaches a single flower to the inflorescence. In the absence of a pedicel, the flowers are described as sessile. Pedicel is also applied to the stem of the infructescence. The word "pedicel" is derived from the latin pediculus, meaning "little foot".

Charles Darwin British naturalist, author of "On the origin of species, by means of natural selection"

Charles Robert Darwin, was an English naturalist, geologist and biologist, best known for his contributions to the science of evolution. His proposition that all species of life have descended over time from common ancestors is now widely accepted, and considered a foundational concept in science. In a joint publication with Alfred Russel Wallace, he introduced his scientific theory that this branching pattern of evolution resulted from a process that he called natural selection, in which the struggle for existence has a similar effect to the artificial selection involved in selective breeding.

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<i>Anacamptis pyramidalis</i> species of plant

Anacamptis pyramidalis, the pyramidal orchid, is a perennial herbaceous plant belonging to the genus Anacamptis of the family Orchidaceae. The scientific name Anacamptis derives from Greek ανακάμτειν 'anakamptein' meaning 'bend forward', while the Latin name pyramidalis refers to the pyramidal form of the inflorescence.

Pollinator

A pollinator is an animal that moves pollen from the male anther of a flower to the female stigma of a flower. This helps to bring about fertilization of the ovules in the flower by the male gametes from the pollen grains.

Coevolution Two or more species influencing each others evolution

In biology, coevolution occurs when two or more species reciprocally affect each other's evolution.

Pollinium

A pollinium is a coherent mass of pollen grains in a plant that are the product of only one anther, but are transferred, during pollination, as a single unit. This is regularly seen in plants such as orchids and many species of milkweeds (Asclepiadoideae). Usage of the term differs: in some orchids two masses of pollen are well attached to one another, but in other orchids there are two halves each of which is sometimes referred to as a pollinium.

Between 1860 and 1868, the life and work of Charles Darwinfrom Orchids to Variation continued with research and experimentation on evolution, carrying out tedious work to provide evidence of the extent of natural variation enabling artificial selection. He was repeatedly held up by his illness, and continued to find relaxation and interest in the study of plants. His studies of insect pollination led to publication of his book Fertilisation of Orchids as his first detailed demonstration of the power of natural selection, explaining the complex ecological relationships and making testable predictions. As his health declined, he lay on his sickbed in a room filled with inventive experiments to trace the movements of climbing plants.

Entomophily

Entomophily or insect pollination is a form of pollination whereby pollen of plants, especially but not only of flowering plants, is distributed by insects. Flowers pollinated by insects typically advertise themselves with bright colours, sometimes with conspicuous patterns leading to rewards of pollen and nectar; they may also have an attractive scent which in some cases mimics insect pheromones. Insect pollinators such as bees have adaptations for their role, such as lapping or sucking mouthparts to take in nectar, and in some species also pollen baskets on their hind legs. This required the coevolution of insects and flowering plants in the development of pollination behaviour by the insects and pollination mechanisms by the flowers, benefiting both groups.

<i>Drakaea</i> genus of plants

Drakaea is a genus of 10 species in the plant family Orchidaceae commonly known as hammer orchids. All ten species only occur in the south-west of Western Australia. Hammer orchids are characterised by an insectoid labellum that is attached to a narrow, hinged stem, which holds it aloft. The stem can only hinge backwards, where the broadly winged column carries the pollen and stigma. Each species of hammer orchid is pollinated by a specific species of thynnid wasp. Thynnid wasps are unusual in that the female is flightless and mating occurs when the male carries a female away to a source of food. The labellum of the orchid resembles a female thynnid wasp in shape, colour and scent. Insect pollination involving sexual attraction is common in orchids but the interaction between the male thynnid wasp and the hammer orchid is unique in that it involves the insect trying to fly away with a part of the flower.

This is a partial list of the writings of Charles Darwin, including his main works.

<i>Angraecum sesquipedale</i> species of plant

Angraecum sesquipedale, also known as Darwin's orchid, Christmas orchid, Star of Bethlehem orchid, and king of the angraecums, is an epiphytic orchid in the genus Angraecum endemic to Madagascar. The orchid was first discovered by the French botanist Louis-Marie Aubert du Petit-Thouars in 1798, but was not described until 1822. It is noteworthy for its long spur and its association with the naturalist Charles Darwin, who surmised that the flower was pollinated by a then undiscovered moth with a proboscis whose length was unprecedented at the time. His prediction had gone unverified until 21 years after his death, when the moth was discovered and his conjecture vindicated. The story of its postulated pollinator has come to be seen as one of the celebrated predictions of the theory of evolution.

<i>Xanthopan</i> species of insect

Xanthopan is a monotypic genus of sphinx moth, with Xanthopan morganii, commonly called Morgan's sphinx moth, as its sole species. It is a very large sphinx moth from East Africa and Madagascar. Little is known about its biology, though the adults have been found to visit orchids.

<i>Fertilisation of Orchids</i> Book by Charles Darwin with full title On the Various Contrivances by Which British and Foreign Orchids Are Fertilised by Insects, and On the Good Effects of Intercrossing

Fertilisation of Orchids is a book by English naturalist Charles Darwin published on 15 May 1862 under the full explanatory title On the Various Contrivances by Which British and Foreign Orchids Are Fertilised by Insects, and On the Good Effects of Intercrossing. Darwin's previous book, On the Origin of Species, had briefly mentioned evolutionary interactions between insects and the plants they fertilised, and this new idea was explored in detail. Field studies and practical scientific investigations that were initially a recreation for Darwin—a relief from the drudgery of writing—developed into enjoyable and challenging experiments. Aided in his work by his family, friends, and a wide circle of correspondents across Britain and worldwide, Darwin tapped into the contemporary vogue for growing exotic orchids.

Catasetum fimbriatum species of plant

Catatsetum fimbriatum is a member of the Orchid family of angiosperms and lives in a warm tropical environment. This plant uses a fascinating strategy to spread its pollen to other flowers via insects, primarily bees. When a pollinator lands on male flowers of C. fimbriatum and stimulates them, pollen is planted onto the back of the pollinator. This assures their gametes will be spread to other flowers the bee visits of the same species.

<i>Das entdeckte Geheimnis der Natur im Bau und in der Befruchtung der Blumen</i> book by Christian Konrad Sprengel

Das entdeckte Geheimnis der Natur im Bau und in der Befruchtung der Blumen by Christian Konrad Sprengel was published in 1793, but received little acclaim during the author's lifetime. Sprengel's ideas were rejected by other naturalists when it was published, but the importance of this work was duly appreciated by Charles Darwin some sixty years later. Darwin's use of Sprengel's ideas and reference to this book in the seminal work on the Fertilisation of Orchids established Sprengel's book as one of the most important works in the fields of floral biology and pollination ecology and its author as a founding father of these fields.

The Different Forms of Flowers on Plants of the Same Species is a book by Charles Darwin first published in 1877. It is the fifth of his six books devoted solely to the study of plants.

Pollination trap

Pollination traps or trap-flowers are plant flower structures that aid the trapping of insects, mainly flies, so as to enhance their effectiveness in pollination. The structures of pollination traps can include deep tubular corollas with downward pointing hairs, slippery surfaces, adhesive liquid, attractants, flower closing and other mechanisms.

<i>Euglossa cordata</i> species of insect

Euglossa cordata is a primitively eusocial orchid bee of the American tropics. The species is known for its green body color and ability to fly distances of over 50 km. Males mostly disperse and leave their home nests, while females have been observed to possess philopatric behavior. Because of this, sightings are rare and little is known about the species. However, it has been observed that adults who pollinate certain species of orchids will become intoxicated during the pollination.

John Traherne Moggridge British botanist and entomologist (1842-1874)

John Traherne Moggridge was a British botanist, entomologist, and arachnologist. A Fellow of the Linnean Society of London, he was known as a keen naturalist with great observational skills, as well as his paintings and illustrations. He wrote several articles on the fertilisation of plants, and his paintings of plants of southern France appeared in Contributions to the Flora of Mentone. His two volume study, Harvesting Ants and Trap-door Spiders, among other observations, confirmed that harvester ants are present in Europe, and was one of the first comprehensive treatments of the burrowing behaviour of trapdoor spiders. He was a correspondent of Charles Darwin, who cited his work in his books Fertilisation of Orchids and The Descent of Man, and Selection in Relation to Sex.

Floral biology is an area of ecological research that studies the evolutionary factors that have moulded the structures, behaviour and physiological aspects involved in the flowering of plants. The field is broad and interdisciplinary and involves research requiring expertise from multiple disciplines that can include botany, ethology, biochemistry, entomology and a range of analytical techniques. A slightly narrower area of research within floral biology is sometimes termed as pollination biology or anthecology.

References

  1. Petra Ballings (2006). "About Orchids". Vumba nature. Archived from the original on 2009-04-22. Retrieved 2009-08-12.
  2. Darwin 1862 , pp.  9–19
  3. Darwin 1862 , pp.  211–214, [http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F800&pageseq=237 222–224