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| [Note Guidelines] Photographer's Note [French] |
Plant
Asystasia gangetica, T. Anderson is a perennial herb of the family Acanthaceae.
The stem is erect, slender, high 30-60 cm, pubescent. It bears opposite leaves entire, more or less hairy, oval. The flowers are grouped in loose racemes, located at ends of stems.
The flower is symmetrical (bilateral symmetry), but somewhat irregular, contrary to what exists in general among Acanthaceae (hence, the name Asystasia = inconsistent - not consistent with the normal phenotype of the family). The petals are welded tube slightly bumpy at first, then individualized in 5 irregular rounded lobes. The stamens are welded to a portion of their length. The flower is white, sometimes tinged with pink or purple, mainly on the lower lip of the corolla.
Origin and area expansion
Asystasia gangetica would originate from the banks of the Ganges, whence come his name, gangetica. This plant is very ubiquitous, present in Africa, Asia and India.
Properties
This plant is reputed to have medicinal properties (eg, Nigeria, using the fight against asthma). It could also be used as a food source (use of the leaves for this purpose in some villages in Central Cameroon, in periods of high scarcity, most common usage, in Kenya and Uganda, in association with beans, sesame peanuts and many other uses in other countries).
Given its power of proliferation, it is sometimes used as plant protectiion of the soil against erosion and as agent for the eradication of other plants that can be harmful to human or agricultural activities.
Environmental Status
In environmental terms, this herb is now considered an invasive plant potentially dangerous to the natural ecosystems, particularly in Australia, Malaysia, Indonesia, Papua New Zealand and Pacific Islands. It is the subject of a warning about this in Australia where it is prohibited to import, although it is not yet officially classified as a global invasive noxious weed.
Photography
The photograph was taken in the afternoon, sunny and quiet. The camera is set to aperture priority mode. The sensitivity is equivalent iso-200 with a focal length of 8 mm. The lens is in close up macro mode. Given the proximity of the subject and to have a sufficient depth of field, aperture is the lowest offered by the lens, f/11, which allows the intense sunlight of the day. With these parameters the calculated speed is 1 / 40 th of a second.
Documentary resources
http://www.weeds.gov.au/publications/guidelines/alert/pubs/a-gangetica.pdf
http://malherbologie.cirad.fr/Advenrun/especes/a/asyco/asyco.html
http://www.flowersofindia.net/catalog/slides/Ganges%20Primrose.html
http://database.prota.org/PROTAhtml/Asystasia%20gangetica_En.htm
http://toptropicals.com/index.htm |
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