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''Drosera regia'', commonly known as the king sundew, is a carnivorous plant in the sundew genus ''Drosera'' endemic to a single valley in South Africa. The genus name ''Drosera'' comes from the Greek word ''droseros'', meaning "dew-covered". The specific epithet ''regia'' is derived from the Latin for "royal", a reference to the "striking appearance" of the species. Individual leaves can reach in length. It has many unusual relict characteristics not found in most other ''Drosera'' species, including woody rhizomes, operculate pollen, and the lack of circinate vernation in scape growth. All of these factors, combined with molecular data from phylogenetic analysis, contribute to the evidence that ''D. regia'' possesses some of the most ancient characteristics within the genus. Some of these are shared with the related Venus flytrap (''Dionaea muscipula''), which suggests a close evolutionary relationship. The tentacle-covered leaves can capture large prey, such as beetles, moths, and butterflies. The tentacles of all ''Drosera'' species are specialised stalked glands on the leaf's upper surface that produce a sticky mucilage. The leaves are considered active flypaper traps that respond to captured prey by bending to surround it. In its native fynbos habitat, the plants compete for space with native marsh grasses and low evergreen shrubs. Of the two known populations of ''D. regia'', the higher altitude site appears to be overgrown and is essentially extirpated. The lower altitude site is estimated to have about 50 mature plants, making it the most endangered ''Drosera'' species, since it is threatened with extinction in the wild. It is often cultivated by carnivorous plant enthusiasts, and a single cultivar has been registered. == Description == ''Drosera regia'' plants are fairly large herbs that produce horizontal woody rhizomes and a crown of large, linear leaves up to long and wide. The leaves possess stalked glands (tentacles) on the upper surface of the lamina along nearly the entire length of the leaf. The leaves lack petioles and stipules, emerging by circinate vernation (uncurling) and tapering to a filiform point. The tentacles and the leaf itself are capable of responding to prey by bending toward insects trapped in the sticky mucilage produced by the glands. Leaves are even capable of folding over themselves several times. Each leaf can possess thousands of tentacles, which can aid in the retention of larger prey when combined with the leaf wrapping tightly around captured insects. In its native habitat, ''D. regia'' has been known to capture large beetles, moths and butterflies. Plants go dormant during the colder season and form a dormant bud, consisting of a tight cluster of short, immature leaves. Plants begin to break dormancy in mid-July with a typical growing season lasting from October to April, though this is variable and plants can continue growing year-round without dormancy.〔Gibson, R. 1999. (''Drosera arcturi'' in Tasmania and a comparison with ''Drosera regia''. ) ''Carnivorous Plant Newsletter'', 28(3): 76–80.〕〔Obermeyer, A. A. 1970. (Droseraceae. ) In L. E. Codd, B. Winter, D. J. B. Killick, and H. B. Rycroft (), ''Flora of South Africa'', 13: 187–201. Department of Agricultural Technical Services, Pretoria, South Africa.〕〔McPherson, S. 2008. ''Glistening Carnivores: The Sticky-leaved Insect-eating Plants.'' Poole, Dorset, England: Redfern Natural History Productions. pp. 154–157. ISBN 978-0-9558918-1-6〕 Individual leaves die back but remain attached to the short stem, clothing the bottom portion of the plant in the blackened dead leaves of former years.〔Stephens, E. L. 1926. A new sundew, ''Drosera regia'' (Stephens), from the Cape Province. ''Transactions of the Royal Society of South Africa'', 13(4): 309–312. 〕 The woody rhizomes produced by the plant are one of the unusual characteristics that it shares only with ''D. arcturi'' in the genus; the absence of woody rhizomes in all other ''Drosera'' is often cited as an indication of the presumed ancient lineage of ''D. regia'' and ''D. arcturi''. ''Drosera regia'' also produces relatively few thick, fleshy roots, which possess root hairs along the terminal . Asexual reproduction of mature plants usually occurs after flowering with new plants arising from the rhizome and roots. After a fire, undamaged roots will often re-sprout new plants.〔〔 ''Drosera regia'' flowers in January and February, producing scapes up to long. The scapes emerge vertically, lacking the circinate vernation of its leaves and all other scapes of the genus ''Drosera'', with the exception of ''D. arcturi''. The scapes consist of two primary branches and bear 5 to 20 (sometimes 30) unscented pink flowers with long petals. Bracts are small, bearing some reduced tentacles. Each flower has three unbranched, spreading styles emerging from the top of the ovary and extending beyond the five erect stamens (15 mm long), which surround the ovary. This arrangement minimizes the chance of self-fertilisation. Studies have shown that the operculate pollen shed in tetrads (fused groups of four pollen grains), characteristics that are similar in the related ''Dionaea muscipula'' (the Venus flytrap) and ''Aldrovanda vesiculosa'', is incompatible with clones, failing to produce seed when plants are self-fertilised. Seeds are brown to black, linear and ornamented with fine network-like markings, and 2 mm long and 0.5 mm in diameter. Seed is shed by the end of March.〔〔〔〔Takahashi, H. and Sohma, K. 1982. Pollen morphology of the Droseraceae and its related taxa. ''Science Reports of the Research Institutes Tohoku University, 4th Series, Biology'', 38: 81–156.〕 The unusual characteristics that set it apart from other species in the genus include the woody rhizome, undivided styles, and the operculate pollen.〔〔Seine, R., and Barthlott, W. 1994. (Some proposals on the infrageneric classification of ''Drosera'' L. ) ''Taxon'', 43: 583–589. 〕 ''Drosera regia'' shares other features with the robust Tasmanian form of ''D. arcturi'', including the lack of stipules and petioles and the non-circinate growth of the scape.〔 It has a diploid chromosome number of 2''n'' = 34, which is unusual for the genus ''Drosera'' and closer to the diploid chromosome number of the Venus flytrap (''Dionaea muscipula''), another member of the Droseraceae.〔Behre, K. 1929. Physiologische und zytologische Untersuchungen über ''Drosera''. ''Planta'', 7: 208–306. 〕〔Kondo, K. 1969. Chromosome numbers of carnivorous plants. ''Bulletin of the Torrey Botanical Club'', 96(3): 322–328. 〕 Variable chromosome counts for ''Dionaea'' from multiple studies include 2''n'' = 30, 32, and 33. Of the ''Drosera'' species with known chromosome counts, most are a multiple of ''x'' = 10. Based on an extensive review of karyotype studies, the botanist Fernando Rivadavia suggested that the base chromosome number for the genus could be 2''n'' = 20, a number that many ''Drosera'' species share including the widespread ''D. rotundifolia''. Exceptions to this base number include the Australian, New Zealand and Southeast Asian ''Drosera'', which have chromosome numbers ranging from 2''n'' = 6 to 64.〔Rivadavia, F. 2005. (New chromosome numbers for ''Drosera'' L. (Droseraceae). ) ''Carnivorous Plant Newsletter'', 34(3): 85–91.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Drosera regia」の詳細全文を読む スポンサード リンク
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