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Gunnera is the sole genus of herbaceous in the family Gunneraceae, which contains 63 species. Some species in this genus, namely those in the subgenus Panke, have extremely large leaves. Species in the genus are variously native to Latin America, Australia, New Zealand, Papuasia, Hawaii, insular Southeast Asia, eastern Africa, and Madagascar. Kew World Checklist of Selected Plant Families The stalks of some species are edible.
The genus Gunnera was named after the Norwegian botanist Johann Ernst Gunnerus. At first it was assigned to the family Haloragaceae, though that presented difficulties that led to the general recognition of the family Gunneraceae, as had been proposed about the beginning of the 20th century. In the meantime, in many publications it had been referred to as being in the Haloragaceae, variously misspelt (as for example "Halorrhagidaceae".) Such references still cause difficulties in consulting earlier works. However, currently Gunnera is firmly assigned to the Monotypic taxon family Gunneraceae.
The type species of the genus is Gunnera perpensa L.
Due to the widespread distribution of Gunnera during the Cretaceous, it was previously thought that the modern disjunct distribution of the genus was a relic of this period. However, phylogenetic analysis indicates that the majority of Gunnera species, even those found on entirely different continents, diverged from each other during the Cenozoic, indicating that the modern distribution of Gunnera is a consequence of long-distance dispersal from South America to other parts of the world, rather than relics of a former cosmopolitan distribution. The only species that diverged prior to the Cenozoic is Gunnera herteri, described from Uruguay and distributed in Uruguay and southeastern Brazil, which is thought to be the most ancient species of the genus, its lineage having diverged during the Late Cretaceous, roughly concurrent with the oldest Gunnera fossil pollen from Peru. The persistence of the Gunnera crown group since the Cretaceous makes it unique among flowering plants, and may have been facilitated by strong niche conservatism, Seed dispersal ability, and being able to aggressively colonize disturbed land.
Only slightly smaller is Gunnera masafuerae of the Juan Fernandez Islands off the coast. They can have leaves up to in width on stout leaf stalks long and thick according to Skottsberg. These leaf stalks or petioles are the thickest of any dicot, and probably also the most massive. On nearby Isla Más Afuera, Gunnera peltata frequently has an upright trunk to in height by thick, bearing leaves up to wide. The Hoja de Pantano ( Gunnera magnifica) of the Andes bears the largest leaf buds of any plant; up to long and thick. The Succulent plant leaf stalks are up to long. The massive inflorescence of small, reddish is up to long and weighs about 13 kg. The flowers of Gunnera species are dimerous (two sepals, two petals (or none), two stamens (or one), and two carpels. Other giant Gunnera species within the subgenus Panke are found throughout the Neotropics and Hawaii. Gunnera insignis is also known by the name "poor man's umbrella" in Costa Rica.
Outside of the subgenus Panke, some Gunnera species have small-to-medium-sized leaves. There are some species with moderately large leaves in Africa ( G. perpensa, in the subgenus Gunnera, syn. subgenus Perpensum); and Southeast Asia ( G. macrophylla, in the subgenus Pseudogunnera), but the others are low-lying, mat-forming plants with small leaves. There are several small species are found in New Zealand, notably G. albocarpa, with leaves only 1–2 cm long, and also in South America, with G. magellanica having leaves 5–9 cm wide on stalks 8–15 cm long. G. herteri, which is Sister group to all other members of the genus and is found in Uruguay and Brazil, also has small leaves.
Some fossil leaf impressions of Gunnera from the Cretaceous of North America have large leaves akin to those of Panke, and G. mexicana, which is sister to all other extant species within Panke, is the northernmost member. For this reason, it has been suggested that Panke originates from South American Gunnera that colonized North America during the Cretaceous and grew into giant forms, with the remaining South American Gunnera evolving into the subgenus Misandra, with a low-lying, matlike growth. During the Cenozoic, the North American Panke would have colonized Hawaii and retreated southwards on the mainland before recolonizing South America. However, more recent phylogenetic evidence suggests that Misandra and Panke diverged only 15 million years ago, much too recent to assign the Cretaceous Gunnera to Panke. Due to this, the large-leaved Cretaceous Gunnera from North America may represent a distinct lineage that convergently evolved giant leaves similar to those of Panke, but did not leave any descendants.
In 2022, it was shown that plants in cultivation under the name Gunnera manicata were actually a hybrid, Gunnera × cryptica.
Gunnera perpensa is a source of traditional medicine in southern Africa, both in veterinary and human ailments, largely in obstetric and digestive complaints, but also as a wound dressing. It also is eaten in various ways, largely the petioles, flower stalks and leaves, fresh and raw, preferably with skins and fibre removed, which is said to remove bitterness, but also cooked. The plant also is said to be used in making a beer.
Species
, Plants of the World Online accepts the following species separated by subgenus:
New Zealand Tasmania New Zealand New Zealand New Zealand New Zealand New Zealand New Zealand incl Chatham Islands New Zealand New Guinea New Zealand Peru, Bolivia Colombia Bolivia, Argentina Colombia, Ecuador Bolivia, Argentina, Chile Colombia Peru, Ecuador Bolivia Robinson Crusoe Island in Chile Colombia, Ecuador, Peru Colombia Colombia, Ecuador Cultivated Colombia Colombia Colombia Colombia Panama, Nicaragua, Costa Rica Costa Rica Kauai in Hawaii Chiapas, Guatemala, Honduras Colombia Colombia S Brazil Peru, Bolivia Alejandro Selkirk Island (Isla Mas Afuera) in Chile Veracruz, Chiapas Colombia Robinson Crusoe Island in Chile Ecuador, Peru Hawaii Peru, Bolivia, Ecuador Venezuela Ecuador Colombia Colombia Bolivia, Argentina Colombia Ecuador, Colombia Venezuela Colombia Ecuador, Colombia Costa Rica, Panama Colombia Colombia Chile, Argentina Venezuela Tierra del Fuego
Cyanobacterial symbiosis
At least some species of Gunnera host Endosymbiont cyanobacteria such as Nostoc punctiforme. The cyanobacteria provide fixed nitrogen to the plant, while the plant provides fixed carbon to the microbe. The bacteria enter the plant via glands found at the base of each leaf stalk and initiate an intracellular symbiosis which is thought to provide the plant with fixed nitrogen in return for fixed carbon for the bacterium. The Nostoc-filled symbiotic tissue makes up just a small portion of the plant's total biomass. Gunnera is the only known genus of angiosperms that hosts cyanobacteria, and the only known land plant with intracellular . Although the endosymbionts enters the cell wall, they do not penetrate the cell membrane. This relationship may provide insights to allow the creation of novel symbioses between crop plants and cyanobacteria, allowing growth in areas lacking fixed nitrogen in the soil.
Uses
The stalks of G. tinctoria ( nalca), from southern Chile and Argentina, are edible. Their principal use is fresh consumption, after peeling, but also they are prepared in salads, liquor or marmalade. Leaves of this species are used in covering curanto (a traditional Chilean food).
(1982). 9780908387328, Delta Books. ISBN 9780908387328
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