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The Info List - Drosera



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DROSERA, commonly known as the SUNDEWS, is one of the largest genera of carnivorous plants , with at least 194 species . These members of the family Droseraceae lure, capture, and digest insects using stalked mucilaginous glands covering their leaf surfaces. The insects are used to supplement the poor mineral nutrition of the soil in which the plants grow. Various species, which vary greatly in size and form, are native to every continent except Antarctica
Antarctica
.

Both the botanical name (from the Greek δρόσος: drosos = "dew, dewdrops") and the English common name (sundew, derived from Latin
Latin
ros solis, meaning "dew of the sun") refer to the glistening drops of mucilage at the tip of each tentacle that resemble drops of morning dew .

CONTENTS

* 1 Characteristics

* 1.1 Habit * 1.2 Leaves and carnivory * 1.3 Flowers and fruit * 1.4 Roots

* 2 Taxonomy and phylogenetics * 3 Reproduction * 4 Distribution * 5 Habitat * 6 Conservation status

* 7 Uses

* 7.1 As a medicinal plant * 7.2 As ornamental plants * 7.3 Nanobiotechnology * 7.4 Other uses

* 8 Chemical constituents * 9 Notes * 10 Sources * 11 External links

CHARACTERISTICS

A tuber of D. zonaria , a tuberous sundew, beginning its winter growth

Sundews are perennial (or rarely annual ) herbaceous plants , forming prostrate or upright rosettes between 1 and 100 cm (0.39 and 39.37 in) in height, depending on the species. Climbing species form scrambling stems which can reach much longer lengths, up to 3 m (9.8 ft) in the case of D. erythrogyne . Sundews have been shown to be able to achieve a lifespan of 50 years. The genus is specialized for nutrient uptake through its carnivorous behavior, for example the pygmy sundew is missing the enzymes (nitrate reductase , in particular) that plants normally use for the uptake of earth-bound nitrates.

HABIT

The genus can be divided into several habits , or growth forms:

* Temperate sundews: These species form a tight cluster of unfurled leaves called a hibernaculum in a winter dormancy period (= Hemicryptophyte ). All of the North American and European species belong to this group. Drosera arcturi from Australia (including Tasmania) and New Zealand is another temperate species that dies back to a horn-shaped hibernaculum. * Subtropical sundews: These species maintain vegetative growth year-round under uniform or nearly uniform climatic conditions. * Pygmy sundews: A group of roughly 40 Australian species, they are distinguished by miniature growth, the formation of gemmae for asexual reproduction , and dense formation of hairs in the crown center. These hairs serve to protect the plants from Australia's intense summer sun. Pygmy sundews form the subgenus Bryastrum . * Tuberous sundews: These nearly 50 Australian species form an underground tuber to survive the extremely dry summers of their habitat, re-emerging in the autumn. These so-called tuberous sundews can be further divided into two groups, those that form rosettes and those that form climbing or scrambling stems. Tuberous sundews comprise the subgenus Ergaleium .

D. derbyensis , from the petiolaris complex

* Petiolaris complex: A group of tropical Australian species, they live in constantly warm but sometimes wet conditions. Several of the 14 species that comprise this group have developed special strategies to cope with the alternately drier conditions. Many species, for example, have petioles densely covered in trichomes , which maintain a sufficiently humid environment and serve as an increased condensation surface for morning dew. The Petiolaris complex comprises the subgenus Lasiocephala .

Although they do not form a single strictly defined growth form, a number of species are often put together in a further group:

* Queensland
Queensland
sundews: A small group of three species (D. adelae , D. schizandra and D. prolifera ), all are native to highly humid habitats in the dim understories of the Australian rainforest.

LEAVES AND CARNIVORY

Leaf
Leaf
and tentacle movement on D. capensis

Sundews are characterised by the glandular tentacles, topped with sticky secretions, that cover their laminae . The trapping and digestion mechanism usually employs two types of glands: stalked glands that secrete sweet mucilage to attract and ensnare insects and enzymes to digest them, and sessile glands that absorb the resulting nutrient soup (the latter glands are missing in some species, such as D. erythrorhiza ). Small prey, mainly consisting of insects, are attracted by the sweet secretions of the peduncular glands. Upon touching these, the prey become entrapped by sticky mucilage which prevents their progress or escape. Eventually, the prey either succumb to death through exhaustion or through asphyxiation as the mucilage envelops them and clogs their spiracles . Death usually occurs within 15 minutes. The plant meanwhile secretes esterase , peroxidase , phosphatase and protease enzymes . These enzymes dissolve the insect and free the nutrients contained within it. This nutrient mixture is then absorbed through the leaf surfaces to be used by the rest of the plant. Drosera
Drosera
Glandular Hair

All species of sundew are able to move their tentacles in response to contact with edible prey. The tentacles are extremely sensitive and will bend toward the center of the leaf to bring the insect into contact with as many stalked glands as possible. According to Charles Darwin , the contact of the legs of a small gnat with a single tentacle is enough to induce this response. This response to touch is known as thigmonasty , and is quite rapid in some species. The outer tentacles (recently coined as "snap-tentacles") of D. burmannii and D. sessilifolia can bend inwards toward prey in a matter of seconds after contact, while D. glanduligera is known to bend these tentacles in toward prey in tenths of a second. In addition to tentacle movement, some species are able to bend their laminae to various degrees to maximize contact with the prey. Of these, D. capensis exhibits what is probably the most dramatic movement, curling its leaf completely around prey in 30 minutes. Some species, such as D. filiformis , are unable to bend their leaves in response to prey. Emergences of an Australian D. indica

A further type of (mostly strong red and yellow) emergence has recently been discovered in