Aquilegia

Aquilegia, commonly known as columbines, is a genus of perennial flowering plants in the family Ranunculaceae. The genus includes between 80 and 400 taxa with natural ranges across the Northern Hemisphere. Natural and introduced populations of Aquilegia exist on all continents but Antarctica. Known for their high physical variability and ease of hybridization, columbines are popular garden plants and have been used to create many cultivated varieties.
Aquilegia typically possess stiff stems and leaves that divide into multiple leaflets. Columbines often have colorful flowers with five sepals and five petals. The petals generally feature nectar spurs which differ in lengths between species. In North America, morphological variations in spurs evolved to suit different pollinators. Some species and varieties of columbines are naturally spurless. In cultivation, varieties bearing significantly altered physical traits such as double flowering are prevalent.
Columbines have been associated with fertility goddesses in ancient Greece and ancient Rome and Christian religious religious concepts. Archeological evidence suggests Aquilegia plants were in cultivation by the 2nd century AD in Roman Britain, and they remain popular in gardens worldwide. Despite often being toxic, columbines have been used by humans as herbal remedies, perfume, and food. Asian traditional medicine practitioners, Indigenous North Americans, and Medieval Europeans have considered portions of the plants to have medicinal uses. Selective breeding and hybridization of columbines has occurred for centuries, with exchanges between Old and New World species creating further diversity.

Etymology

The 1st-century AD Greek writer Dioscorides called columbines Isopyrum, a name used presently applied to another genus, Isopyrum. In the 12th century, the abbess and polymath Hildegard of Bingen referred to the plants as agleya from which the genus's name in German, Akelei, derives. The first use of aquilegia with regards to columbines was in the 13th century by Albertus Magnus. In the 15th and 16th centuries, the names Colombina, Aquilina, and Aquileia came into use. With the Swedish biologist Carl Linnaeus's 1753 Species Plantarum, the formal name for the genus became Aquilegia, though limited use of Aquilina persisted in scientific usage until at least 1901.
Several scientific and common names for the genus Aquilegia derive from its appearance. The genus name Aquilegia may come from the Latin word for "eagle", aquila, in reference to the petals' resemblance to eagle talons. Another possible etymology for Aquilegia is a derivation from the Latin aquam legere, aquilegium, or aquilex in reference to the profusion of nectar in the spurs. The most common English-language name, columbine, likely originates in the dove-like appearance of the sepals.
There are a number of other common names for Aquilegia across different languages. In English, these include granny's bonnet for some plants in the species Aquilegia vulgaris. The association of columbine with the 1999 Columbine High School massacre has led to use of the names aquilegia and granny's bonnet used in horticultural circles as a means of avoiding the stigmatized name. In French, the word ancolie is the common name for Aquilegia, while individual members of the genus have been called gants-de-Notre-Dame. In Italian, amor-nascoto has been used.

Description

Aquilegia is a genus of herbaceous, perennial flowering plants in the family Ranunculaceae. The genus is highly variable in appearance. Though they are perennials, certain species are short-lived, with some exhibiting lifespans more similar to biennials and others only flourishing for six to eight years. Following a dormant period in the winter, columbines will grow foliage and have a brief flowering period. Some columbines bloom the first year after sowing, others will bloom in their second. Later, seed heads will emerge and split, sowing new seed. The foliage lives through the summer before wilting and dying going into the fall.
Aquilegia plants grow from slim, woody rootstocks that comprise the perennial portion of the plants. One or more annual aerial stems rise from the rootstocks each growing season, ultimately drying out following fruiting. Leaves can grow in both basal and cauline arrangements. Leaves emanating from closer to the plant's core are generally borne on flexible petioles, while leaves further from the core generally lack petioles. The compound leaves of Aquilegia are generally ternate, biternate, or triternate.
The flowering stems emerge from rosettes during the spring and summer. Each inflorescence appears at the terminus of an aerial stem and can reach long. Depending on the species, an inflorescence will feature one to ten of either cymes or solitary flowers. Flower morphology varies across the genus, but all columbine flowers emerge from buds that are initially nodding. Flowers can be monochromatic or display multiple colors. The typical flower color for columbines is blue in shades ranging into purple and nearly black shades. Blue flowering is especially the norm in European columbines, where only A. aurea possesses yellow flowers. In North America, yellow and red flowers are typical, with blue and blue-purple flowers almost exclusive to high-altitude species.
The perianth of Aquilegia flowers generally comprise five sepals that look like petals and five petals. Each petal typically comprises two portions: a blade, which are broad and project towards the front of the flower, and a nectar spur, a nectar-bearing structure which projects backwards. The hollow spurs attract pollinators and give columbine flowers a distinctive appearance. Depending on the species, spurs can have a hooked, horn-like appearance, with straight to coiled spurs also present in the genus. Some columbines, such as A. ecalcarata, are naturally spurless. Recessive spurlessness individuals and populations can also be found within typically spurred species.
The reproductive portions of columbine flowers comprise the stamen and gynoecium. The stamina, which bear the anthers from which pollen emerges, form whorls of five around the gynoecia. The total number of stamen varies between species. There are generally scale-shaped staminodes between the stamen and female pistil structures. The flowers undergo three stages of anthesis: a premale stage, where the flower perianth is open but the anthers are not dehisced ; the male stage where with the perianth present and the anthers dehiscenced, and a postmale stage where the anthers have withered but the perianth remains.
Aquilegia are bisexual and capable of self-pollination, through either or both autogamy and geitonogamy. Autogamy has been observed as the primary fertilization mechanism in A. paui. A. formosa and A. eximia may exhibit adichogamy, where male and female organs do not operate simultaneously to prevent self-fertilization. Fertilization via cross pollination also occurs in Aquilegia, with pollinators carrying pollen from one flower to the stigma of another.
Aquilegia fruit are follicles. These follicles have a split on one side and terminate with a curling tip known as a beak. Columbine seeds are generally obovoid with black, smooth exteriors. Columbine seeds are in a dormant state at the point of sowing. In cold storage, A. formosa seeds have remained viable for at least three years. Seed germination is primarily dependent on temperature, with seeds typically requiring a multi-month period of summer temperatures followed by a multi-week to multi-month exposure to winter temperatures prior to germinating once temperatures warm with the arrival of spring. This prevents seedlings from emerging until there are survivable environmental conditions.
The chromosome number for columbines is 2n=14. Individual plants have been recorded with other anomalous chromosome numbers, ranging up to 2n=32. It is possible that B chromosomes impact the phenotype and the fertility of individual plants that possess them.

Phytochemistry

Among Aquilegia that are cyanophores like A. vulgaris, the cyanogenic glycosides compounds dhurrin and triglochinin have been observed. Cyanogenic glycosides generally taste bitter and can be toxic to animals and humans. Ingestion of of fresh A. vulgaris leaves by a human was observed as causing convulsions, respiratory distress, and heart failure. A child who consumed 12 A. vulgaris flowers experienced weakness of the limbs, cyanosis, drowsiness, and miosis; all symptoms abated after three hours. Mature seeds and roots contain toxins that, if consumed, are perilous to human heart health.
The presence of the antibacterial flavonoid compound isocytisoside has been observed in A. vulgaris. Polyphenols, primarily flavonoids, are the main component of hydroethanolic extract from A. oxysepala. These compounds function as antioxidants. A study of A. oxysepala extract found it has a good scavenging effect on DPPH, superoxide anion, and hydroxyl radicals, but a poor scavenging capacity towards hydrogen peroxide. For all these, ascorbic acid has a superior scavenging effect to the extract.
In flowering plants, the presence of phenylpropanoids can serve as protection from ultraviolet light and as a signaling mechanism towards pollinators. A study that examined A. formosa flowers determined that the petals and sepals had uniform levels of UV-resistant phenylpropanoids.

Ecology

Despite its toxicity and in the absence of incentives, some animals consume the fruit and leaves of columbines. Consumption by mammals is not considered a component of the Aquilegia reproductive cycle but has been observed. In the case of the endangered A. paui, one study found that 30% of all fruit was lost to predation by the Southeastern Spanish ibex.
In the Northeastern United States and Eastern Canada, A. canadensis serves as the host plant for the butterfly Erynnis lucilius. In two periods, the first from April to June and the second from July to September, the butterflies lay their eggs on the underside of the columbine leaves. The latterly laid brood overwinters as caterpillars in the plant litter around the columbine. In the Western United States, Bombus occidentalis has been observed nectar robbing from A. coerulea by opening or using holes cut in the spurs.
Also in North America, three leaf miner species in the genus Phytomyza lay their eggs on Aquilegia: P. aquilegiana in the east, P. aquilegivora in the Midwestern United States, and P. columbinae in the west. Collectively known as the columbine leaf miners, white trails or splotches on leaves indicate where the larvae consumed the tissue between the leaves' surfaces. The larvae will cut through the leaves, pupating in small puparium on the leaves' undersides. Adults pierce the leaves with their ovipositors to access liquids in the plants, leaving marks. Another Phytomyza columbine leaf miner, P. ancholiae, is native to France.
Originally from Europe, Pristiphora rufipes is now also found in Canada and the United States. After developing from eggs laid on columbine leaves in late spring, the green larvae will eat the leaves from the outside in during their active period from April to June. In cases where many larvae are on the same plant, only the stem and flowers may go uneaten. The larvae mature within a few weeks, after which they drop from the plants and pupate in cocoons.
Several fungi attack columbine foliage, including Ascochyta aquilegiae, Cercospora aquilegiae, and Septoria aquilegiae. The fungus-like oomycete species Peronospora aquilegiicola, a type of downy mildew, originated in East Asian Aquilegia and Semiaquilegia populations. It was first reported on columbines in the United Kingdom in 2013, resulting in discussion about quarantining measures to prevent its spread to Continental Europe.