Description
Drosera regia plants are fairly large herbs that produce horizontal woody rhizomes and a crown of large, linear leaves up to 70 cm (28 in) long and 2 cm (0.8 in) 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. 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.
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 15 cm (6 in). 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 40 cm (16 in) 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 2–3 cm (0.8–1.2 in) 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.
The unusual characteristics that set it apart from other species in the genus include the woody rhizome, undivided styles, and the operculate pollen. 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 2n = 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. Variable chromosome counts for Dionaea from multiple studies include 2n = 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 2n = 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 2n = 6 to 64.
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