Rafflesia Arnoldii is a species of flowering plant in the parasitic genus Rafflesia. It is noted for producing the largest individual flower on Earth. It has a strong and unpleasant odor of decaying flesh. It is native to the rainforests of Sumatra and Borneo. Although there are some plants with larger flowering organs like the titan arum (Amorphophallus titanum) and talipot palm (Corypha umbraculifera), those are technically clusters of many flowers.
Rafflesia Arnoldii is one of the three national flowers in Indonesia, where it is known locally as the puspa langka or Padma paksasa. The other two being the white jasmine (Jasminum sambac) and moon orchid (Phalaenopsis amabilis). The first person to discover Rafflesia was the ill-fated French explorer Louis Auguste Deschamps in Java between 1791 and 1794, but his notes and illustrations were seized by the British in 1803 and were not available to western science until 1861.
Thailand, Rafflesia can be seen in Khao Sok National Park where the flowers are numbered and monitored by the park rangers. The regional name of Rafflesia Arnoldii is kerubut in Sumatra, cendawan biriang in the Minangkabau language in kecamatan (‘district’) of Pandam Gadang and “corpse flower” by the local people.
Although Rafflesia is a vascular plant, it lacks any observable leaves, stems or even roots, and does not have chlorophyll properties. It lives as a holoparasite on vines of the genus Tetrastigma. Similar to fungi, individuals grow as a mass of thread-like strands of tissue completely embedded within and in intimate contact with surrounding host cells from which nutrients and water are obtained. It can only be seen outside the host plant when it is ready to reproduce; the only part of Rafflesia that is identifiable as distinctly plant-like are the flowers, though even these are unusual since they attain massive proportions, have a reddish-brown colouration, and stink of rotting flesh. The flower of Rafflesia Arnoldii grows to a diameter of around one meter (3.3 feet), weighing up to 11 kilograms. These flowers emerge from very large, cabbage-like, maroon or dark brown buds typically about 30 cm (12 in) wide, but the largest flower bud ever recorded found at Mount Sago, Sumatra in May 1956 was 43 cm (17 in) in diameter. Indonesian researchers often refer to the bud as a ‘knop’ (knob).
Rafflesia Arnoldii is found in both secondary and primary rainforests. The only host plant species of Rafflesia Arnoldii is Tetrastigma leucostaphylum in West Sumatra. Tetrastigma are themselves parasites of a sort, using the strength and upright growth of other surrounding plants to reach the light. The trees that Tetrastigma uses to climb up to light, are relatively limited in number of species, although they are generally the closest tree to the vine. The buds take many months to develop and the flower lasts for just a few days. The flowers are gonochorous – either male or female, thus both flowers are needed for successful pollination.
When Rafflesia is ready to reproduce, a tiny bud forms outside the root or stem of its host and develops over a period of a year. The cabbage-like head that develops eventually opens to reveal the flower. The stigmas or stamens are attached to a spiked disk inside the flower. A foul smell of rotting meat attracts flies and beetles. To pollinate successfully, the flies and beetles must visit both the male and female plants, in that order. The fruit produced are round berries filled with numerous minute seeds.
The flies like Drosophila colorata, Chrysomya megacephala and Sarcophaga haemorrhoidalis visit the late flowers. Black ants of the genus Euprenolepis may feed on the developing flower buds, perhaps killing them.
It’s conservation has not been assessed for the IUCN Red List. Ecotourism is thought to be a main threat to the species, at locations which are regularly visited by tourists the number of flower buds produced per year has decreased.