Rafflesia

Rafflesia is a genus of parasitic flowering plants. It contains approximately 28 species (including four incompletely characterized species as recognized by Willem Meijer in 1997), all found in Southeast Asia, mainly in Indonesia, Malaysia, Thailand and the Philippines. It was first discovered by Louis Deschamps in Java between 1791 and 1794, but his notes and illustrations, seized by the British in 1803, were not available to western science until 1861. It was later found in the Indonesian rainforest in Bengkulu, Sumatra by an Indonesian guide working for Joseph Arnold in 1818, and named after Sir Stamford Raffles, the leader of the expedition. The plant has no stems, leaves or roots. It is a holoparasite of vines in the genus Tetrastigma (Vitaceae), spreading its absorptive organ, the haustorium, inside the tissue of the vine. The only part of the plant that can be seen outside the host vine is the five-petalled flower. In some species, such as Rafflesia arnoldii, the flower may be over 100 centimetres (39 in) in diameter, and weigh up to 10 kilograms (22 lb). Even one of the smallest species, R. baletei, has 12 cm diameter flowers. The flowers look and smell like rotting flesh, hence its local names which translate to 'corpse flower' or 'meat flower' (see below). The foul odor attracts insects such as flies, which transport pollen from male to female flowers. Most species have separate male and female flowers, but a few have hermaphroditic flowers. Little is known about seed dispersal. However, tree shrews and other forest mammals eat the fruits and disperse the seeds. Rafflesia is the official state flower of Indonesia, where it is known as puspa langka (rare flower) or padma paksasa (giant flower), of Sabah state in Malaysia, and of Surat Thani Province in Thailand. In Thailand, Rafflesia can be observed in Khao Sok National Park where the flowers are numbered and monitored by the park rangers. Rafflesia are also remarkable for showing a large horizontal transfer of genes from their host plants. This is well known among bacteria, but not higher organisms. The name 'corpse flower' applied to Rafflesia can be confusing because this common name also refers to the titan arum (Amorphophallus titanum) of the family Araceae. Moreover, because Amorphophallus has the world's largest unbranched inflorescence, it is sometimes mistakenly credited as having the world's largest flower. Both Rafflesia and Amorphophallus are flowering plants, but they are only distantly related. Rafflesia arnoldii has the largest single flower of any flowering plant, at least in terms of weight. Amorphophallus titanum has the largest unbranched inflorescence, while the talipot palm (Corypha umbraculifera) forms the largest branched inflorescence, containing thousands of flowers; the talipot is monocarpic, meaning the individual plants die after flowering. Comparison of mitochondrial DNA (mtDNA) sequences of Rafflesia with other angiosperm mtDNA indicated this parasite evolved from photosynthetic plants of the order Malpighiales. Another study from that same year confirmed this result using both mtDNA and nuclear DNA sequences, and showed the three other groups traditionally classified in Rafflesiaceae were unrelated. A more recent study more specifically found Rafflesia and its relatives to be embedded within the family Euphorbiaceae, which is surprising, as members of that family typically have very small flowers. According to their analysis, the rate of flower size evolution was more or less constant throughout the family except at the origin of Rafflesiaceae, where the flowers rapidly evolved to become much larger before reverting to the slower rate of change. Species native to Borneo include Rafflesia arnoldii, Rafflesia cantleyi, Rafflesia hasseltii, Rafflesia keithii, Rafflesia kerrii, Rafflesia pricei, and Rafflesia tengku-adlinii. R. arnoldii boasts the world's largest single bloom. Some endemic Borneon species, such as R. keithii, begin blooming at night and start to decompose only two to three days later. The time from bud emergence to flowering is six to nine months. Male and female flowers must be open simultaneously for pollination to occur, hence successful pollination and fruit production are quite rare. In addition to habitat loss, these reproductive limitations are contributing factors to why many species are endangered. R. keithii is found along the eastern slopes of Mount Kinabalu in the Lohan Valley of Sabah. Rafflesia tuan-mudae is endemic to only Gunung Gading National Park in Sarawak.