Gunnera

Gunnera is a genus of herbaceous flowering plants, some of them gigantic. The genus is the only member of the family Gunneraceae.

The 40-50 species vary enormously in leaf size. Gunnera manicata, native to the Serra do Mar mountains of southeastern Brazil, is perhaps the largest species, with leaves typically 1.5-2 m (5-6 ft) wide, but exceptionally long, up to 3.4 m (11 ft), borne on thick, succulent leaf stalks (petioles) up to 2.5 m (8 ft) long. It germinates best in very moist, but not wet, conditions and temperatures of 22 to 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 5 inches) in width on stout leaf stalks 1.5 m (5 ft) long and 11 cm (4.5 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 (10–12 in) thick, bearing leaves up to 2 m (6 ft 4 inches) wide. G. magnifica of the Colombian Andes bears the largest leaf buds of any plant; up to 60 cm (2 ft) long and 40 cm (16 inches) thick. The succulent leaf stalks are up to 2.7 m (8 ft 10 inches) long. The massive inflorescence of small, reddish flowers is up to 2.3 m (7 ft 6 inches) 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.

Commonly known as "giant rhubarb".



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


 * Selected species
 * Gunnera albocarpa
 * Gunnera arenaria
 * Gunnera densiflora
 * Gunnera dentata
 * Gunnera flavida
 * Gunnera hamiltonii
 * Gunnera kauaiensis
 * Gunnera magellanica
 * Gunnera magnifica
 * Gunnera manicata
 * Gunnera masafuerae
 * Gunnera monoica
 * Gunnera perpensa
 * Gunnera petaloïdea
 * Gunnera prorepens
 * Gunnera tinctoria

Cyanobacterial Symbiosis
In nature, all Gunnera plants form a symbiosis with a nitrogen-fixing cyanobacteria, thought to be exclusively Nostoc punctiforme. The bacteria invade 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 higher 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) 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.