Editing Drosera (section)

== Description ==
[[File:DroseraZonariaTuber2-.jpg|thumb|upright|A tuber of ''[[Drosera zonaria|D. zonaria]]'', a tuberous sundew, beginning its winter growth]]
Sundews are [[perennial plant|perennial]] (or rarely [[Annual plant|annual]]) [[herbaceous plant]]s, typically forming prostrate or upright rosettes between {{convert|1|and|100|cm||abbr=on}} in height, depending on the species. Climbing species form scrambling stems which can reach much longer lengths, up to {{convert|3|m|ft|abbr=on}} in the case of ''[[Drosera erythrogyne|D.&nbsp;erythrogyne]]''.<ref name="Mann-2001">{{cite journal |last1=Mann |first1=Phill |title=The world's largest Drosera |journal=Carnivorous Plant Newsletter |date=2001 |volume=30 |issue=3 |page=79 |url=http://www.cephalotus.net/article.aspx?cid=12&y=2001&m=10&d=22 |access-date=2022-08-17 |archive-date=2011-09-29 |archive-url=https://archive.today/20110929000000/http://www.cephalotus.net/article.aspx?cid=12&y=2001&m=10&d=22 |url-status=dead }}</ref> Sundews have been shown to be able to achieve a lifespan of 50 years.<ref name="Barthlott-2004">{{cite book |last1=Barthlott |first1=Wilhelm |last2=Porembski |first2=Stefan |last3=Seine |first3=Rüdiger |last4=Theisen |first4=Inge |title=Karnivoren Biologie und Kultur fleischfressender Pflanzen |date=1 June 2004 |publisher=Verlag Eugen Ulmer |location=Stuttgart (Hohenheim) |isbn=9783800141449}}</ref>{{rp|102}} The genus is specialized for [[nutrient]] uptake through its carnivorous behavior, for example the pygmy sundew is missing the [[enzyme]]s ([[nitrate reductase]], in particular)<ref name="Karlsson-1992">{{cite journal |last1=Karlsson |first1=PS |last2=Pate |first2=JS |title=Contrasting effects of supplementary feeding of insects or mineral nutrients on the growth and nitrogen and phosphorous economy of pygmy species of Drosera. |journal=Oecologia |date= 1992 |volume=92 |issue=1 |pages=8–13 |doi=10.1007/BF00317256 |pmid=28311806 | bibcode=1992Oecol..92....8K | s2cid=13038192 }}</ref> that plants normally use for the uptake of earth-bound nitrates.

=== Growth form<!--as in growth form, NOT Habitat, as in location--> ===
The genus can be divided into several [[habit (biology)|habits]], or growth forms:
* Temperate sundews: These species form a tight cluster of unfurled leaves called a [[hibernaculum (botany)|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 [[Gemma (botany)|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 ''[[Drosera subg. Bryastrum|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 ''[[Drosera subg. Ergaleium|Ergaleium]]''.
[[File:Drosera derbyensis ne1.JPG|thumb|''[[Drosera derbyensis|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 [[Petiole (botany)|petioles]] densely covered in [[trichome]]s, which maintain a sufficiently humid environment and serve as an increased [[condensation]] surface for morning dew. The ''Petiolaris'' complex comprises the subgenus ''[[Drosera subg. Lasiocephala|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 sundews: A small group of three species (''[[Drosera adelae|D.&nbsp;adelae]]'', ''[[Drosera schizandra|D.&nbsp;schizandra]]'' and ''[[Drosera prolifera|D.&nbsp;prolifera]]''), all are native to highly humid habitats in the dim understories of the Australian rainforest.

=== Leaves and carnivory ===
[[File:Drosera capensis bend.JPG|thumb|upright|Leaf and tentacle movement on ''[[Drosera capensis|D. capensis]]'']]
Sundews are characterised by the glandular tentacles, topped with sticky secretions, that cover their [[Leaf|leaves]]. 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 [[Sessility (botany)|sessile]] [[gland]]s that absorb the resulting nutrient soup (the latter glands are missing in some species, such as ''[[Drosera erythrorhiza|D.&nbsp;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 [[Spiracle (arthropods)|spiracle]]s. Death usually occurs within 15 minutes.<ref name="Darwin-1875">{{cite book| author-first=Charles |author-last=Darwin | title=Insectivorous Plants
| year=1875| location=London|publisher= John Murray  |url=http://darwin-online.org.uk/EditorialIntroductions/Freeman_InsectivorousPlants.html |access-date= March 14, 2022}}</ref> The plant meanwhile secretes [[esterase]], [[peroxidase]], [[phosphatase]] and [[protease]] [[enzymes]].<ref name="Barthlott-2004" />{{rp|41}} 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.
 [[File:Drosera Glandular Hair.jpg|thumb|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.<ref name="Darwin-1875"/> This response to touch is known as [[thigmonasty]], and is quite rapid in some species. The outer tentacles (recently coined as "snap-tentacles") of ''[[Drosera burmanni|D.&nbsp;burmanni]]'' and ''[[Drosera sessilifolia|D.&nbsp;sessilifolia]]'' can bend inwards toward prey in a matter of seconds after contact, while ''[[Drosera glanduligera|D.&nbsp;glanduligera]]'' is known to bend these tentacles in toward prey in tenths of a second.<ref>Hartmeyer, I. & Hartmeyer, S., (2005) Drosera glanduligera: Der Sonnentau mit "Schnapp-Tentakeln", DAS TAUBLATT (GFP) 2005/2: 34-38</ref> In addition to tentacle movement, some species are able to bend their leaves to various degrees to maximize contact with the prey. Of these, ''[[Drosera capensis|D.&nbsp;capensis]]'' exhibits what is probably the most dramatic movement, curling its leaf completely around prey in 30 minutes. Some species, such as ''[[Drosera filiformis|D.&nbsp;filiformis]]'', are unable to bend their leaves in response to prey.<ref name="D'Amato, Peter-1998">{{cite book | author=D'Amato, Peter | title=The Savage Garden: Cultivating Carnivorous Plants | publisher=Ten Speed Press | location=Berkeley, California | year=1998 | isbn=978-0-89815-915-8 | title-link=The Savage Garden: Cultivating Carnivorous Plants }}</ref>

[[File:DroseraIndicaEmergences.JPG|thumb|Emergences of an Australian ''[[Drosera indica|D. indica]]'']]
A further type of (mostly strong red and yellow) leaf coloration has recently been discovered in a few Australian species (''[[Drosera hartmeyerorum|D. hartmeyerorum]]'', ''[[Drosera indica|D. indica]]''). Their function is not known yet, although they may help in attracting prey.

The leaf morphology of the species within the genus is extremely varied, ranging from the sessile [[:File:Leaf morphology no title.png|ovate]] leaves of ''D. erythrorhiza'' to the bipinnately divided [[:File:Leaf morphology no title.png|acicular]] leaves of ''[[Drosera binata|D. binata]]''.

While the exact physiological mechanism of the sundew's carnivorous response is not yet known, some studies have begun to shed light on how the plant is able to move in response to mechanical and chemical stimulation to envelop and digest prey. Individual tentacles, when mechanically stimulated, fire action potentials that terminate near the base of the tentacle, resulting in rapid movement of the tentacle towards the center of the leaf.<ref>{{Cite journal|last1=Williams|first1=Stephen E.|last2=Pickard|first2=Barbara G.|date=1972|title=Receptor potentials and action potentials in Drosera tentacles|journal=Planta|volume=103|issue=3|pages=193–221|doi=10.1007/bf00386844|pmid=24481555|bibcode=1972Plant.103..193W |s2cid=2155695|issn=0032-0935}}</ref><ref name="Williams-1980">{{cite book |last1=Williams |first1=S. E. |last2=Pickard |first2=B. G. |chapter= The Role of Action Potentials in the Control of Capture Movements of Drosera and Dionaea|title= Plant Growth Substances 1979|series=Proceedings in Life Sciences |date=1980 |pages=470–480 |doi=10.1007/978-3-642-67720-5_48|isbn=978-3-642-67722-9 }}</ref> This response is more prominent when marginal tentacles further away from the leaf center are stimulated. The tentacle movement response is achieved through auxin-mediated [[acid growth]]. When action potentials reach their target cells, the plant hormone [[auxin]] causes protons (H<sup>+</sup> ions) to be pumped out of the plasma membrane into the cell wall, thereby reducing the pH and making the cell wall more acidic.<ref>{{Cite journal|last1=Rayle|first1=D. L.|last2=Cleland|first2=R. E.|date=1992-08-01|title=The Acid Growth Theory of auxin-induced cell elongation is alive and well.|journal=Plant Physiology|volume=99|issue=4|pages=1271–1274|doi=10.1104/pp.99.4.1271|issn=0032-0889|pmid=11537886|pmc=1080619}}</ref> The resulting reduction in pH causes the relaxation of the cell wall protein, expansin, and allows for an increase in cell volume via osmosis and turgor. As a result of differential cell growth rates, the sundew tentacles are able to achieve movement towards prey and the leaf center through the bending caused by expanding cells.<ref>{{Cite journal|last=Hooker|first=Henry D.|date=1917|title=Mechanics of Movement in Drosera rotundifolia|jstor=2479748|journal=Bulletin of the Torrey Botanical Club|volume=44|issue=8|pages=389–403|doi=10.2307/2479748}}</ref>  Among some ''Drosera'' species, a second bending response occurs in which non-local, distant tentacles bend towards prey as well as the bending of the entire leaf blade to maximize contact with prey. While mechanical stimulation is sufficient to achieve a localized tentacle bend response, both mechanical and chemical stimuli are required for the secondary bending response to occur.<ref>{{Cite journal|last1=Krausko|first1=Miroslav|last2=Perutka|first2=Zdeněk|last3=Šebela|first3=Marek|last4=Šamajová|first4=Olga|last5=Šamaj|first5=Jozef|last6=Novák|first6=Ondřej|last7=Pavlovič|first7=Andrej|date=March 2017|title=The role of electrical and jasmonate signalling in the recognition of captured prey in the carnivorous sundew plant Drosera capensis|journal=The New Phytologist|volume=213|issue=4|pages=1818–1835|doi=10.1111/nph.14352|issn=1469-8137|pmid=27933609|doi-access=free}}</ref>

=== Flowers and fruit ===
[[File:DroseraKenneallyiFlora.jpg|thumb|Flower of ''[[Drosera kenneallyi|D. kenneallyi]]'']]
The flowers of sundews, as with nearly all carnivorous plants, are held far above the leaves by a long stem. This physical isolation of the flower from the traps is commonly thought to be an adaptation meant to avoid trapping potential [[pollinator]]s. The mostly unforked [[inflorescence]]s are [[raceme|spikes]], whose flowers open one at a time and usually only remain open for a short period. Flowers open in response to light intensity (often opening only in direct sunlight), and the entire inflorescence is also [[heliotropism|heliotropic]], moving in response to the sun's position in the sky.
[[File:Drosera with flower stem.jpg|alt=Multiple drosera plants with long flower stalks|thumb|Multiple ''drosera'' plants with long flower stalks]]
The [[Symmetry (biology)#Radial symmetry|radially symmetrical]] ([[actinomorphic]]) flowers are always [[Perfect flower|perfect]] and have five parts (the exceptions to this rule are the four-petaled ''[[Drosera pygmaea|D. pygmaea]]'' and the eight to 12-petaled ''[[Drosera heterophylla|D. heterophylla]]''). Most of the species have small flowers (<1.5&nbsp;cm or 0.6&nbsp;in). A few species, however, such as ''[[Drosera regia|D. regia]]'' and ''[[Drosera cistiflora|D. cistiflora]]'', have flowers {{convert|4|cm|in|abbr=on}} or more in diameter.<ref name="D'Amato, Peter-1998" /> In general, the flowers are white or pink. Australian species display a wider range of colors, including orange (''[[Drosera callistos|D. callistos]]''), red (''[[Drosera adelae|D. adelae]]''), yellow (''[[Drosera zigzagia|D. zigzagia]]'') or metallic violet (''[[Drosera microphylla|D. microphylla]]'').

The [[Ovary (plants)|ovary]] is [[Ovary (plants)|superior]] and develops into a [[Dehiscence (botany)#Fruit dehiscence|dehiscent]] [[Capsule (fruit)|seed capsule]] bearing numerous tiny seeds. The [[pollen]] grain type is compound, which means four [[microspore]]s (pollen grains) are stuck together with a protein called [[callose]].{{Citation needed|date=May 2012}}

=== Roots ===
[[File:Drosera anglica ne2.jpg|thumb|''Drosera anglica'' with prey]]
The root systems of most ''Drosera'' are often only weakly developed or have [[vestigiality|lost their original functions]].<ref name="Adlassnig-2005">{{cite journal |last1=Adlassnig |first1=Wolfram |last2=Peroutka |first2=Marianne |last3=Lambers |first3=Hans |last4=Lichtscheidl |first4=Irene K. |date=July 2005 |title=The Roots of Carnivorous Plants |url=https://link.springer.com/article/10.1007/s11104-004-2754-2 |journal=Plant and Soil |volume=274 |issue=1–2 |pages=127–140 |doi=10.1007/s11104-004-2754-2|bibcode=2005PlSoi.274..127A |s2cid=5038696 }}</ref> They are relatively useless for nutrient uptake, and they serve mainly to absorb water and to anchor the plant to the ground; they have long [[root hair|hair]]s.<ref name="Adlassnig-2005"/>

A few South African species use their roots for water and food storage. Some species have wiry root systems that remain during frosts if the stem dies. Some species, such as ''D. adelae'' and ''[[Drosera hamiltonii|D. hamiltonii]]'', use their roots for asexual propagation, by sprouting plantlets along their length. Some Australian species form underground [[corm]]s for this purpose, which also serve to allow the plants to survive dry summers. The roots of pygmy sundews are often extremely long in proportion to their size, with a 1-cm (0.4-in) plant extending roots over {{convert|15|cm|in|abbr=on}} beneath the soil surface. Some pygmy sundews, such as ''[[Drosera lasiantha|D. lasiantha]]'' and ''[[Drosera scorpioides|D. scorpioides]]'', also form [[adventitious root]]s as supports.

''[[Drosera intermedia|D. intermedia]]'' and ''[[Drosera rotundifolia|D. rotundifolia]]'' have been reported to form [[arbuscular mycorrhiza]]e, which penetrate the plant's tissues,<ref name="Wang-2006">{{cite journal |last1=Wang |first1=B. |last2=Qiu |first2=Y.-L. |title=Phylogenetic distribution and evolution of mycorrhizas in land plants |journal=Mycorrhiza |date=July 2006 |volume=16 |issue=5 |pages=299–363 |doi=10.1007/s00572-005-0033-6|pmid=16845554 |bibcode=2006Mycor..16..299W |s2cid=30468942 }}</ref> they also host fungi like [[endophyte]]s to collect nutrients when they grow in poor soil and form [[symbiosis|symbiotic relationships]].<ref>{{cite journal |last1=Quilliam |first1=Richard S. |last2=Jones |first2=David L. |title=Fungal root endophytes of the carnivorous plant Drosera rotundifolia |url=https://link.springer.com/article/10.1007/s00572-009-0288-4 |journal=Mycorrhiza |date=June 2010 |volume=20 |issue=5 |pages=341–348 |doi=10.1007/s00572-009-0288-4 |pmid=20012108 |bibcode=2010Mycor..20..341Q |s2cid=11825262 }}</ref>