Gunnera

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Gunnera
Gunnera tinctoria 2.jpg
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.
Species

See text.

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.

Gunnera manicata Devon, England
Gunnera insignis Costa Rica

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

Distribution[edit]

South America.[1]

Ireland: Occasional of the west coast.[2] Clare Island, Co. Mayo.[3]

Selected species[edit]

Cyanobacterial symbiosis[edit]

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[4] 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[edit]

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.

References[edit]

  1. ^ Webb, D.A. et al. 1996. An Irish Flora. Dundalgan Press. ISBN 0-85221-131-7
  2. ^ Webb, D.A. et al. 1996. An Irish Flora. Dundalgan Press. ISBN 0-85221-131-7
  3. ^ Guiry, M.D. et al 2007.New Survey of Clare Island. Volume 6: The Freshwater and Terrestrial Algae. Royal Irish Academy. ISBN 978-1-904890-31-7
  4. ^ Bergman, B.; Johansson, C.; Soderback, E. (1992). "The Nostoc-Gunnera symbiosis". New Phytologist 122 (3): 379. doi:10.1111/j.1469-8137.1992.tb00067.x. 

External links[edit]