Rafflesia arnoldii

Rafflesia arnoldii








Kingdom : Plantae
Division : Magnoliophyta
Class : Magnoliopsida
Order : Malpighiales
Family : Rafflesiaceae
Genus : Rafflesia
Species : R. arnoldii
Binomial name : Rafflesia arnoldii R.Br.

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, the Titan Arum and Talipot palm, but these are technically clusters of many flowers. It occurs only in the rainforests of Sumatra and Borneo in the Indonesia Archipelago.

Molecular studies in 2007 have resulted in the final taxonomy of Rafflesia arnoldii which has been assigned to the family of Euphorbiaceae (Davis et al. 2007).


Description
Several species of Rafflesia grow in the jungles of southeast Asia, including the Philippines. Many of them threatened or endangered. Rafflesia arnoldii is the largest; its flower attains a diameter of nearly a meter (3 ft) and can weigh up to 11 kilograms (24 lb).

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.


Specimen of Rafflesia arnoldii at the Kyoto Botanical Garden.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 have continued. However, steps are being taken to conserve the forests of Sumatra and Borneo.

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 near 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 event 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