Drosera gigantea
Encyclopedia
Drosera gigantea, the giant sundew, is an erect perennial
tuber
ous species in the carnivorous plant
genus Drosera that is endemic to Western Australia
. It grows in sandy soils at the margins of swamps and near granite outcrops
along the Western Australian coast from Albany
north to just south of Geraldton
. D. gigantea produces small shield-shaped leaves along many lateral branches that look like a small tree. Individual plants can grow up to 0.2–1 m (0.656167979002625–3.3 ft) tall. Because of its tall, tree-like form, it is considered one of the largest Drosera species. It is also easily cultivated and enjoys damp, humid conditions often provided in greenhouses. White flowers emerge from August to November. The red tubers of this species can grow to be 3.8 cm (1.5 in) in diameter and may be a metre below ground.
D. gigantea was first described and named by John Lindley
in his 1839 A sketch of the vegetation of the Swan River Colony
. In 1992, N. G. Marchant
and Allen Lowrie
described a new subspecies
, D. gigantea subsp. geniculata, that grows to 0.45 m (1.5 ft) tall in black sandy soils near Perth
and to its south. Jan Schlauer disagreed with Marchant and Lowrie's decision to give the new taxon
a rank of subspecies and thus published a new combination of the taxon at the rank of variety in a 1996 issue of the Carnivorous Plant Newsletter
. He argued that subspecies should be reserved for those occasions where allopatric
, or geographically isolated, speciation
occurred and varieties are best used in cases where sympatric speciation
is suspected. Others disagree with this assessment, as Western Australia's online flora database, FloraBase
, lists the varietal taxon (D. gigantea var. geniculata (N.G.Marchant & Lowrie) Schlauer) as a synonym of the subspecies.
The shoots of D. gigantea have been found to contain the rare secondary metabolite
s naphthoquinone
, glucoside
s, droserone, hydroxydroserone, and plumbagin
. It is thought that the glucosides are responsible for the brown colour of the plant.
Perennial plant
A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...
tuber
Tuber
Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to survive the winter or dry months and provide energy and nutrients for regrowth during the next growing season and they are a means of asexual reproduction...
ous species in the carnivorous plant
Carnivorous plant
Carnivorous plants are plants that derive some or most of their nutrients from trapping and consuming animals or protozoans, typically insects and other arthropods. Carnivorous plants appear adapted to grow in places where the soil is thin or poor in nutrients, especially nitrogen, such as acidic...
genus Drosera that is endemic to Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
. It grows in sandy soils at the margins of swamps and near granite outcrops
Granite outcrops of Western Australia
Granite outcrops of Western Australia are inselbergs and monoliths made from granite that are found across much of Western Australia. Rising abruptly from the surrounding landscape they create a variety of microhabitats for plants, and provide seasonal resources and refuge for a range of animals....
along the Western Australian coast from Albany
Albany, Western Australia
Albany is a port city in the Great Southern region of Western Australia, some 418 km SE of Perth, the state capital. As of 2009, Albany's population was estimated at 33,600, making it the 6th-largest city in the state....
north to just south of Geraldton
Geraldton, Western Australia
Geraldton is a city and port in Western Australia located north of Perth in the Mid West region. Geraldton has an estimated population at June 2010 of 36,958...
. D. gigantea produces small shield-shaped leaves along many lateral branches that look like a small tree. Individual plants can grow up to 0.2–1 m (0.656167979002625–3.3 ft) tall. Because of its tall, tree-like form, it is considered one of the largest Drosera species. It is also easily cultivated and enjoys damp, humid conditions often provided in greenhouses. White flowers emerge from August to November. The red tubers of this species can grow to be 3.8 cm (1.5 in) in diameter and may be a metre below ground.
D. gigantea was first described and named by John Lindley
John Lindley
John Lindley FRS was an English botanist, gardener and orchidologist.-Early years:Born in Catton, near Norwich, England, John Lindley was one of four children of George and Mary Lindley. George Lindley was a nurseryman and pomologist and ran a commercial nursery garden...
in his 1839 A sketch of the vegetation of the Swan River Colony
A Sketch of the Vegetation of the Swan River Colony
A Sketch of the Vegetation of the Swan River Colony, also known by its standard botanical abbreviation Sketch Veg. Swan R., is an 1839 article by John Lindley on the flora of the Swan River Colony...
. In 1992, N. G. Marchant
N. G. Marchant
Neville Graeme Marchant is a retired Western Australian botanist. He was formerly the Director of the Western Australian Herbarium.Marchant began working for the Western Australian Herbarium at the age of 15, as a laboratory assistant to Government Botanist Charles Gardner. Later he attended the...
and Allen Lowrie
Allen Lowrie
Allen Lowrie is a West Australian botanist. He is living in Duncraig, a Perth suburb, is married and has two daughters.Lowrie, originally a businessman and inventor, got in contact with the carnivorous flora of western Australia in the late sixties and worked on it as an amateur...
described a new subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
, D. gigantea subsp. geniculata, that grows to 0.45 m (1.5 ft) tall in black sandy soils near Perth
Perth, Western Australia
Perth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....
and to its south. Jan Schlauer disagreed with Marchant and Lowrie's decision to give the new taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
a rank of subspecies and thus published a new combination of the taxon at the rank of variety in a 1996 issue of the Carnivorous Plant Newsletter
Carnivorous Plant Newsletter
The Carnivorous Plant Newsletter is the official publication of the International Carnivorous Plant Society , the largest such organization in the world.-History and editorship:...
. He argued that subspecies should be reserved for those occasions where allopatric
Allopatric speciation
Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration...
, or geographically isolated, speciation
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
occurred and varieties are best used in cases where sympatric speciation
Sympatric speciation
Sympatric speciation is the process through which new species evolve from a single ancestral species while inhabiting the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms whose ranges overlap or are even identical, so that...
is suspected. Others disagree with this assessment, as Western Australia's online flora database, FloraBase
FloraBase
FloraBase is a public access web-based database of the flora of Western Australia. It provides authoritative scientific information on 12,978 taxa, including descriptions, maps, images, conservation status and nomenclatural details...
, lists the varietal taxon (D. gigantea var. geniculata (N.G.Marchant & Lowrie) Schlauer) as a synonym of the subspecies.
The shoots of D. gigantea have been found to contain the rare secondary metabolite
Secondary metabolite
Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism. Unlike primary metabolites, absence of secondary metabolities does not result in immediate death, but rather in long-term impairment of the organism's...
s naphthoquinone
Naphthoquinone
Naphthoquinone is a class of natural phenols based on the C6-C4 skeleton.1,4-Naphthoquinone can be viewed as derivatives of naphthalene through the replacement of two hydrogen atoms by two ketone groups....
, glucoside
Glucoside
A glucoside is a glycoside that is derived from glucose. Glucosides are common in plants, but rare in animals. Glucose is produced when a glucoside is hydrolysed by purely chemical means, or decomposed by fermentation or enzymes....
s, droserone, hydroxydroserone, and plumbagin
Plumbagin
Plumbagin or 5-hydroxy-2-methyl-1,4-naphthoquinone is an organic compound with the chemical formula . It is regarded as a toxin.Plumbagin is a yellow dye, formally derived from naphthoquinone....
. It is thought that the glucosides are responsible for the brown colour of the plant.