Kamis, 27 Maret 2008

Rafflesia arnoldii

Rafflesia arnoldii

Rafflesia arnoldii is a member of the genus Rafflesia. It is noted for producing the largest individual flower on earth. There are some plants with larger flowering organs, Amorphophallus for example, but these are technically clusters of many flowers. It occurs only in the rainforests of Sumatra and Borneo in the Indonesia Archipelago.

from Wikipedia

Several species of Rafflesia grow in the jungles of southeast Asia, many of them threatened or endangered. Rafflesia arnoldii is the largest; its flower attains a diameter of nearly a meter and can weigh up to 11 kilograms. Not only is it the world's largest flower, but it is also one of the most bizarre and improbable organisms on the planet.

It lives as a parasite on the Tetrastigma vine, as its host, which grows only in primary (undisturbed) rainforests. While many parasites appear like normal plants, Rafflesia lacks any observable leaves, roots, or even stems. Likened to fungi, Rafflesia individuals grow as thread-like strands of tissue completely embedded within and in intimate contact with surrounding host cells from which nutrients and water are obtained. Perhaps the only part of Rafflesia that is identifiable as distinctly plant-like are the flowers; although, even these are bizarre because they attain massive proportions and are usually reddish-brown and stink of rotting flesh. The flower is pollinated by flies attracted by its scent.

Rafflesia arnoldii is rare and fairly hard to locate. It is especially difficult to see in flower; the buds take many months to develop and the flower lasts for just a few days. How many of these strange plants still survive is unknown, but as the remaining primary forests of Borneo and Sumatra disappear, it can only be assumed that their numbers are dwindling. Many are known to be nearing extinction. Some environmentalists are thinking of a way to recreate the species' environment, in an effort to stimulate a recovery in the population of this endangered species. This has proved unsuccessful so far, but the efforts are still there.

Pollination is a rare event due to several factors. The flowers are unisexual and single sites usually produce either male or female flowers. Therefore, in order to have effective pollination, male flowers must be in close proximity to, and open at the same time, as the female flowers so that flies can transfer the pollen.

While male and female individuals could be closely spaced, flower bud mortality is 80-90% per site thereby reducing the chance of co-flowering two individuals. Furthermore, the flower lifespan is only 5-7 days. Also, the current population distributions are fragmented due to habitat destruction. So, successful reproduction relies on the unlikely even that a male and female would bloom during the same 5-7 days and that a fly could carry pollen between the often widely separated populations.

Although technically a member of the plant kingdom, Rafflesia arnoldii challenges traditional definitions of what a plant is because it lacks chlorophyll and is therefore incapable of photosynthesis (as are all members of its family, Rafflesiaceae).


The rafflesia is an interesting flower, and not just because of its large size,
almost 1 meter in diameter. Unlike most plants it does not make its own food. It
is a parasite which grows inside a species of grape vine in Malaysia and
Indonesia. Only the flowers come to the outside. The flower smells like
rotting meat to attract flies. The flies carry pollen from the male flower to
the female flower. The female flower produces many, many tiny black seeds,
which is good because the chances of landing in a suitable site to grow (on a
vine of the right kind) are small.

You can find botanical information on the Rafflesia family in Watson and
Dallwitz "The Families of Flowering Plants" at http://www.keil.ukans.edu/delta/
angio/www/rafflesi.htm this site.

You can visit via the internet a place (with pictures) where research is done on
rafflesia at http://www.fsh.ukm.my/fsh/dept/bb/raff/raffles.htm this site.



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