Gunnera

Gunnera
Gunnera tinctoria at the San Francisco Botanical Garden at Strybing Arboretum
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Core eudicots
Order:	Gunnerales
Family:	Gunneraceae
Genus:	Gunnera L.
The range of the genus Gunnera
Synonyms
Milligania Hook.f., rejected name Panke Molina Pankea Oerst.

Gunnera is a genus of herbaceous flowering plants, the only member of the family Gunneraceae. Some species have extremely large leaves. It is native to Latin America, Australia, New Zealand, Papuasia, Hawaii, insular Southeast Asia, Africa, and Madagascar. The stalks of a cultivar from South America are edible and usually eaten raw.. It lives symbiotically with Nostoc punctiforme, a species of cyanobacteria (or "blue-green algae"). Apparently the microbe provides fixed nitrogen to the plant, while the plant provides fixed carbon to the microbe.

Description

The 40–50 species vary enormously in leaf size. The Giant Rhubarb, or Campos des Loges (Gunnera manicata), native to the Serra do Mar mountains of southeastern Brazil, is perhaps the largest species, with leaves typically 1.5 to 2.0 meters (4.9 to 6.6 ft) long, not including the thick, succulent leaf stalk (petiole) of up to 2.5 meters (8.2 feet) in length. The width is typically 2.5 meters (8.2 feet), but on two separate occasions cultivated specimens (In Berkeshire, England in 2011 and at Narrowwater, Ulster, Ireland in 1903) produced leaves fully 3.3 meters (11 feet) in width, making these leaves quite probably the largest of all dicot leaves. The seeds germinate best in very moist, but not wet, conditions and temperatures of 22–29 °C.

Only slightly smaller is G. masafuerae of the Juan Fernandez Islands off the Chilean coast. They can have leaves up to 2.9 m (9 ft 6 in) in width on stout leaf stalks 1.5 m (4.9 ft) long and 11 cm (4.3 in) thick according to Skottsberg. On nearby Isla Más Afuera, G. peltata frequently has an upright trunk to 5.5 m (18 ft) in height by 25–30 cm (9.8–11.8 in) thick, bearing leaves up to 2 m (6 ft 7 in) wide. The Hoja de Pantano (G. magnifica) of the Colombian Andes bears the largest leaf buds of any plant; up to 60 cm (2.0 ft) long and 40 cm (16 in) thick. The succulent leaf stalks are up to 2.7 m (8 ft 10 in) long. The massive inflorescence of small, reddish flowers is up to 2.3 m (7 ft 7 in) long and weighs about 13 kg. Other giant Gunnera species are found throughout the Neotropics and Hawaii.

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.

Gunnera manicata Devon, England

Gunnera insignis Costa Rica

This genus was named after the Norwegian botanist Johann Ernst Gunnerus.

Species

2

Cyanobacterial symbiosis

In nature, all Gunnera plants form a symbiosis with nitrogen-fixing cyanobacteria, thought to be exclusively Nostoc punctiforme. 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. This intracellular interaction is unique in flowering plants and 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 (nalcas), from Southern Chile and Argentina, are edible. Their principal use is fresh consumption, but also they are prepared in salads, liquor or marmalade. Leaves of this species are used in covering curanto (a traditional Chilean food).

Gunnera perpensa is used as a source of traditional medicine in Southern Africa.

External links

• The Gunnera Gallery
• Gunnera magellanica pictures from Chilebosque
• Global Invasive Species database Gunnera tinctoria
• Medicinal plant details Gunnera perpensa
• Gunnera on Achill Island [1]