The column, or technically the gynostemium, is a reproductive structure that can be found in several plant families: Aristolochiaceae and Stylidiaceae. It is derived from the fusion of both male and female parts into a single organ; this means that the style and stigma of the pistil, with the filaments and one or more anthers, are all united. The stigma is pointing downwards after resupination; this stigma has the form of a small bowl, the clinandrium, a viscous surface embedding the single anther. On top of it all is the anther cap. Sometimes there is a small extension or little beak to the median stigma lobe, called rostellum. Column wings may project laterally from the stigma; the column foot is formed by the attachment of the lip to the basal protruding part of the column. One speaks of a mentum if the lateral sepals are basally adnate; the column both releases pollen and receives it for fertilization. In the Orchidaceae family, unlike all other flowering plants, the single male anther at the tip of the column produces pollen, not free and powdery but held in waxy masses of two, four or six pellets called pollinia.
The transfer of pollinia from one flower to another, though efficient, is reliant upon one particular species of arthropods and it can be catastrophic for the population if its pollinator disappears from the community
Ophrys apifera, known in Europe as the bee orchid, is a perennial herbaceous plant belonging to the family Orchidaceae. It is remarkable as an example of sexually-deceptive pollination and floral mimicry as well as of a highly-selective and evolved plant-pollinator relationship. Ophrys apifera grows to a height of 15–50 centimetres; this hardy orchid develops small rosettes of leaves in autumn. They continue to grow during winter. Basal leaves are ovate or oblong-lanceolate, upper leaves and bracts are ovate-lanceolate and sheathing; the plant blooms from mid-April in continental Europe, but in the United Kingdom it flowers June to July. A flower spike is composed from one to twelve flowers; the flowers have large sepals, with a central green rib and colour varying from white to pink, while petals are short, yellow to greenish. The labellum is trilobed, with two pronounced humps on the hairy lateral lobes, the median lobe is hairy and similar to the abdomen of a bee; the labellum is remarkable for displaying at least four distinct colours, in addition to the two colours of the sepals and petals.
Pattern of labellum colouration is quite variable. The gynostegium is with an elongated apex. Chromosomes 2n=36 Ophrys apifera is widespread across central and southern Europe, as well as North Africa and the Middle East, its range stretches from Portugal and Denmark east to Iran and the Caucasus. It is quite common in the Mediterranean region eastwards to the Black Sea, but is less common in its northern range being uncommon or local in Germany and Ireland. In the UK, it has a distinct southeastern preference, it has been found in the southwest of England in Butleigh near Glastonbury in Somerset. It is common in the northeast of England and in recent years large numbers have appeared in the grass verges surrounding the Metro Centre in Gateshead. In Scotland, it was thought to be extinct, but was rediscovered in Ayrshire in 2003. In some countries the plants have protected status, they are unusual in that in some years they appear in great numbers sometimes only reappear after an absence of many years.
Ophrys apifera grows on semi-dry turf, in grassland, on limestone, calcareous dunes or in open areas in woodland. It prefers calcareous soils, in bright dim light, it is a major colonizer of sites disturbed by human activity, such as old quarries, roadside verges and airfields. O. apifera is one of the most European orchid species to establish itself within towns and cities. Ophrys apifera relies upon a symbiotic relationship with mycorrhizal fungi in the genus Tulasnella, to extract sufficient nutrient from the soil it grows in; this makes it vulnerable to chemicals fungicides, but other chemical applications which could reduce the prevalence of Tulasnella fungi. Ophrys apifera is the only species of the genus Ophrys which preferentially practices self-pollination; the flowers are exclusively self-pollinating in the northern ranges of the plant's distribution, but pollination by the solitary bee Eucera longicornis occurs in the Mediterranean area. In this case the plant attracts these insects by producing a scent that mimics the scent of the female bee.
In addition, the lip acts. Pollen transfer occurs during the ensuing pseudocopulation; the flowers emit allomones that attract the bee species Eucera pulveraceae. Eucera longicornis males have been observed attempting to copulate with the flowers, it is believed that male bees would preferentially select orchids with the most bee-like lips and attempt to mate with them, transferring pollen in the process. Ophrys apifera is the County flower of Bedfordshire; the name Ophrys derives from the Greek word ophrys, meaning "eyebrow", while the Latin specific epithet apifera means "bee-bearing" or "bee-bringing" and refers to the bee-shaped lip of the orchid. The genus Ophrys is the most species-rich genus of orchids in Europe and the Mediterranean with over 200 species, according to'Orchids of Britain and Europe' by Pierre Delforge. Ophrys apifera var. apifera Ophrys apifera var. bicolor Ophrys apifera var. botteronii Ophrys apifera var. friburgensis Ophrys apifera var. immaculata Ophrys apifera var. trollii Floral parts display the presence of quercetin and kaempferol glycosides, which are supposed to be acylated, as well as cinnamic acid derivatives.
The pink outer tepals show the presence of anthocyanins. Media related to Ophrys apifera at Wikimedia Commons Data related to Ophrys apifera at Wikispecies Biolib Ophrys apifera Ophrys apifera | Plants of the World Online
The Orchidaceae are a diverse and widespread family of flowering plants, with blooms that are colourful and fragrant known as the orchid family. Along with the Asteraceae, they are one of the two largest families of flowering plants; the Orchidaceae have about 28,000 accepted species, distributed in about 763 genera. The determination of which family is larger is still under debate, because verified data on the members of such enormous families are continually in flux. Regardless, the number of orchid species nearly equals the number of bony fishes and is more than twice the number of bird species, about four times the number of mammal species; the family encompasses about 6–11% of all seed plants. The largest genera are Bulbophyllum, Epidendrum and Pleurothallis, it includes Vanilla–the genus of the vanilla plant, the type genus Orchis, many cultivated plants such as Phalaenopsis and Cattleya. Moreover, since the introduction of tropical species into cultivation in the 19th century, horticulturists have produced more than 100,000 hybrids and cultivars.
Orchids are distinguished from other plants, as they share some evident, shared derived characteristics, or synapomorphies. Among these are: bilateral symmetry of the flower, many resupinate flowers, a nearly always modified petal, fused stamens and carpels, small seeds. All orchids are perennial herbs, they can grow according to two patterns: Monopodial: The stem grows from a single bud, leaves are added from the apex each year and the stem grows longer accordingly. The stem of orchids with a monopodial growth can reach several metres in length, as in Vanda and Vanilla. Sympodial: Sympodial orchids have a front and a back; the plant produces a series of adjacent shoots, which grow to a certain size and stop growing and are replaced. Sympodial orchids grow laterally following the surface of their support; the growth continues by development of new leads, with their own leaves and roots, sprouting from or next to those of the previous year, as in Cattleya. While a new lead is developing, the rhizome may start its growth again from a so-called'eye', an undeveloped bud, thereby branching.
Sympodial orchids may have visible pseudobulbs joined by a rhizome, which creeps along the top or just beneath the soil. Terrestrial orchids may form corms or tubers; the root caps of terrestrial orchids are white. Some sympodial terrestrial orchids, such as Orchis and Ophrys, have two subterranean tuberous roots. One is used as a food reserve for wintry periods, provides for the development of the other one, from which visible growth develops. In warm and humid climates, many terrestrial orchids do not need pseudobulbs. Epiphytic orchids, those that grow upon a support, have modified aerial roots that can sometimes be a few meters long. In the older parts of the roots, a modified spongy epidermis, called velamen, has the function of absorbing humidity, it can have a silvery-grey, white or brown appearance. In some orchids, the velamen includes spongy and fibrous bodies near the passage cells, called tilosomes; the cells of the root epidermis grow at a right angle to the axis of the root to allow them to get a firm grasp on their support.
Nutrients for epiphytic orchids come from mineral dust, organic detritus, animal droppings and other substances collecting among on their supporting surfaces. The base of the stem of sympodial epiphytes, or in some species the entire stem, may be thickened to form a pseudobulb that contains nutrients and water for drier periods; the pseudobulb has a smooth surface with lengthwise grooves, can have different shapes conical or oblong. Its size is variable; some Dendrobium species have long, canelike pseudobulbs with short, rounded leaves over the whole length. With ageing, the pseudobulb becomes dormant. At this stage, it is called a backbulb. Backbulbs still hold nutrition for the plant, but a pseudobulb takes over, exploiting the last reserves accumulated in the backbulb, which dies off, too. A pseudobulb lives for about five years. Orchids without noticeable pseudobulbs are said to have growths, an individual component of a sympodial plant. Like most monocots, orchids have simple leaves with parallel veins, although some Vanilloideae have reticulate venation.
Leaves may be ovate, lanceolate, or orbiculate, variable in size on the individual plant. Their characteristics are diagnostic, they are alternate on the stem folded lengthwise along the centre, have no stipules. Orchid leaves have siliceous bodies called stegmata in the vascular bundle sheaths and are fibrous; the structure of the leaves corresponds to the specific habitat of the plant. Species that bask in sunlight, or grow on sites which can be very dry, have thick, leathery leaves and the laminae are covered by a waxy cuticle to retain their necessary water supply. Shade-loving species, on the other hand, have thin leaves; the leaves of most orchids are perennial, that is, they live for several years, while others those with plicate leaves as in Catasetum, shed them annually and de
According to APG II, the Asclepiadaceae known as milkweed family, is a former plant family now treated as a subfamily in the Apocynaceae. They form a group of perennial herbs, twining shrubs, lianas or trees but notably contain a significant number of leafless stem succulents; the name comes from the type genus Asclepias. There are 348 genera, with about 2,900 species, they are located in the tropics to subtropics in Africa and South America. The florally advanced tribe Stapeliae within this family contains the familiar stem succulent genera such as Huernia and Hoodia, they are remarkable for the complex mechanisms they have developed for pollination, which independently parallel the unrelated Orchidaceae in the grouping of their pollen into pollinia. The fragrance from the flowers called "carrion", attracts flies; the flies pollinate the flowers. Many new hybrids have been formed due to the unique fertilization method of the flowers. Endress, M. E. and P. V. Bruyns, "A revised classification of the Apocynaceae s.l.", Botanical Review, 66: 1–56, doi:10.1007/BF02857781 Stapeliads.info Field Manual for Seed Collectors,Royal Botanic Gardens, Kew Asclepiad info from ig-ascleps.org Asclepiadaceae Family The Genera of Asclepiadoideae and Periplocoideae Asclepiadaceae in BoDD – Botanical Dermatology Database
Asclepias asperula is a species of milkweed native to the Southwestern United States and northern Mexico. Its common names include antelope horns, green-flowered milkweed, spider antelope horns, it is a perennial plant growing to 0.3–0.9 m tall, with clustered greenish-yellow flowers with maroon highlights. It blooms from April through June, favors quickly-draining soil, higher in inorganic matter, such as sand and rock chips, it can grow in clay, if provided with adequate drainage and frequent-enough dryness. Moisture level demands and tolerance depend upon the subspecies and ecotype; the plant has a deep taproot so it needs to have the deepest-possible pot if grown in a container and should not be waterlogged. Asclepias asperula is divided into two subspecies: asperula and capricornu, with the latter occurring in moister conditions and having wider leaves; this helps to explain conflicting information about cold hardiness, moisture tolerance, cardenolide levels when many sources are compared that do not mention the subspecies division.
Subspecies asperula occurs in drier and hotter habitat, thus its narrower leaves and lower maximum height. It also has a higher cardenolide level and lower tolerance of colder growing zones than subspecies capricornu. Subspecies asperula may be referred to colloquially as "spider milkweed" and subspecies capricornu may be referred to colloquially as "antelope horns". However, sometimes subspecies asperula is referred to as antelope horns; this species may require a species of solitary bee, large and strong enough to be able to pry open its flowers for successful pollination. Like several other species of milkweed, A. asperula is a food for monarch butterfly caterpillars. Along with being a source of nutrition for monarchs, the plants contain toxic cardiac glycosides that the monarchs retain, making them unpalatable and poisonous to predators. For the same reason, A. asperula can be poisonous to livestock and other animals, including humans. Native Plant Information Network
Pollen is a fine to coarse powdery substance comprising pollen grains which are male microgametophytes of seed plants, which produce male gametes. Pollen grains have a hard coat made of sporopollenin that protects the gametophytes during the process of their movement from the stamens to the pistil of flowering plants, or from the male cone to the female cone of coniferous plants. If pollen lands on a compatible pistil or female cone, it germinates, producing a pollen tube that transfers the sperm to the ovule containing the female gametophyte. Individual pollen grains are small enough to require magnification to see detail; the study of pollen is called palynology and is useful in paleoecology, paleontology and forensics. Pollen in plants is used for transferring haploid male genetic material from the anther of a single flower to the stigma of another in cross-pollination. In a case of self-pollination, this process takes place from the anther of a flower to the stigma of the same flower. Pollen is used as food and food supplement.
However, because of agricultural practices, it is contaminated by agricultural pesticides. Pollen itself is not the male gamete; each pollen grain contains a generative cell. In flowering plants the vegetative tube cell produces the pollen tube, the generative cell divides to form the two sperm cells. Pollen is produced in the microsporangia in the male cone of a conifer or other gymnosperm or in the anthers of an angiosperm flower. Pollen grains come in a wide variety of shapes and surface markings characteristic of the species. Pollen grains of pines and spruces are winged; the smallest pollen grain, that of the forget-me-not, is around 6 µm in diameter. Wind-borne pollen grains can be as large as about 90–100 µm. In angiosperms, during flower development the anther is composed of a mass of cells that appear undifferentiated, except for a differentiated dermis; as the flower develops, four groups of sporogenous cells form within the anther. The fertile sporogenous cells are surrounded by layers of sterile cells that grow into the wall of the pollen sac.
Some of the cells grow into nutritive cells that supply nutrition for the microspores that form by meiotic division from the sporogenous cells. In a process called microsporogenesis, four haploid microspores are produced from each diploid sporogenous cell, after meiotic division. After the formation of the four microspores, which are contained by callose walls, the development of the pollen grain walls begins; the callose wall is broken down by an enzyme called callase and the freed pollen grains grow in size and develop their characteristic shape and form a resistant outer wall called the exine and an inner wall called the intine. The exine is. Two basic types of microsporogenesis are recognised and successive. In simultaneous microsporogenesis meiotic steps I and II are completed prior to cytokinesis, whereas in successive microsporogenesis cytokinesis follows. While there may be a continuum with intermediate forms, the type of microsporogenesis has systematic significance; the predominant form amongst the monocots is successive.
During microgametogenesis, the unicellular microspores undergo mitosis and develop into mature microgametophytes containing the gametes. In some flowering plants, germination of the pollen grain may begin before it leaves the microsporangium, with the generative cell forming the two sperm cells. Except in the case of some submerged aquatic plants, the mature pollen grain has a double wall; the vegetative and generative cells are surrounded by a thin delicate wall of unaltered cellulose called the endospore or intine, a tough resistant outer cuticularized wall composed of sporopollenin called the exospore or exine. The exine bears spines or warts, or is variously sculptured, the character of the markings is of value for identifying genus, species, or cultivar or individual; the spines may be less than a micron in length referred to as spinulose, or longer than a micron referred to as echinate. Various terms describe the sculpturing such as reticulate, a net like appearance consisting of elements separated from each other by a lumen.
The pollen wall protects the sperm. The pollen grain surface is covered with waxes and proteins, which are held in place by structures called sculpture elements on the surface of the grain; the outer pollen wall, which prevents the pollen grain from shrinking and crushing the genetic material during desiccation, is composed of two layers. These two layers are the tectum and the foot layer, just above the intine; the tectum and foot layer are separated by a region called the columella, composed of strengthening rods. The outer wall is constructed with a resistant biopolymer called sporopollenin. Pollen apertures are regions of the pollen wall that may involve exine thinning or a significant reduction in exine thickness, they allow shrinking and swelling of the grain caused by changes in moisture content. Elongated apertures or furrows in the pollen grain are called sulci. Apertures that are more circular are called pores. Colpi and pores are major features in the identification of classes of pollen.
Pollen may be referre