{{Short description|Species of flowering plant}} {{about||another species cultivated as rocket or arugula see|Eruca sativa}} {{Speciesbox |image = Diplotaxis tenuifolia Sturm32.jpg |genus = Diplotaxis (plant) |species = tenuifolia |authority = (L.) DC. }}
'''''Diplotaxis tenuifolia''''' is a species of flowering plant in the mustard family known by the common name '''perennial wall-rocket'''. It is native to Europe and western Asia, where it grows on disturbed ground and roadsides, and it can now be found throughout much of the temperate world where it has naturalized. In recent years it has increasingly been cultivated to produce salad leaves, which are marketed as '''wild rocket''' in Britain or '''arugula''' in the US. It is easily confused with garden rocket, which has similar uses.
==Description== Perennial wall-rocket is a glabrous herb with an erect or sprawling habit, that grows up to 1.3 m tall, with a solid, almost woody terete stem and spreading branches. The deeply pinnate leaves are up to 12 cm long and often rather fleshy, with a peppery taste and a musty smell.<ref name=rich>{{cite book| last = Rich| first = T.C.G.| year = 1991| title = Crucifers of Great Britain and Ireland | place = London| publisher = Botanical Society of the British Isles| isbn = 0901158208| page = 100}}</ref> thumb|The leaves are typically deeply divided, almost pinnate
In the British Isles, it flowers from May to September<ref name="rich"/> (or through October in a warm year).<ref>{{cite web |last1=Not a Horticulturist |title=Tag: Diplotaxis Tenuifolia |url=https://notahorticulturist.com/tag/diplotaxis-tenuifolia/ |publisher=WordPress.com|access-date=15 October 2022}}</ref> In Spain, it can be seen flowering between April and December.<ref name="Flora Iberica"/> The inflorescence is a branched raceme up to 30 cm long with up to 30 flowers, each of which has 4 free bright yellow petals up to 15 mm long, and 4 free yellow/brown sepals up to 7.5 mm long. Each flower has 6 stamens and a single style.<ref name=Rose>{{cite book |last1=Rose |first1=Francis |title=The Wild Flower Key |date=2006 |publisher=Frederick Warne |location=London|isbn=978-0-7232-5175-0}}</ref><ref name=Stace>{{cite book |last1=Stace |first1=C.A. |title=New Flora of the British Isles |date=2019 |location=Suffolk |isbn=978-1-5272-2630-2}}</ref> thumb|Front view of a flower thumb|Side view of the flowers and buds
The fruit is a straight, flat silique (pod) up to five centimeters long. The pedicels are shorter than the fruits and ascend at an acute angle to the stem. Above the receptacle is a short (2 mm) stalk (or stipe) below the pod (a useful feature for separating this species from annual wall-rocket). The seeds are arranged in 2 rows, or staggered in a zigzag pattern, towards the centre of the pod, which in turn consists of 2 valves, so a cross-section of the fruit shows 4 seeds in total. This is a distinguishing feature of the genus ''Diplotaxis'', although it is not always easy to see, as plants are not self-pollinating, so ripe seeds do not always develop.<ref name="rich" /> thumb|The seeds are arranged in two rows within each valve of the fruit
== Taxonomy == The original name (basionym) of perennial wall-rocket is ''Sisymbrium tenuifolium'', published by Linnaeus in 1755,<ref name=GBIF>{{cite web |last1=Global Biodiversity Information Facility |title=''Diplotaxis tenuifolia'' (L.) DC. |url=https://www.gbif.org/species/5376426 |access-date=6 October 2022}}</ref> but it was transferred to the new genus ''Diplotaxis'' by de Candolle in 1821. It has been given many other names (synonyms) over the years, within the diverse genera ''Arabis'' (rockcresses), ''Brassica'' (mustards), ''Crucifera'', ''Eruca'' (rockets), ''Erysimum'' (wallflowers) and ''Sinapis'' (charlock), which reflects the complex history of crucifer taxonomy. A full list is maintained by the [https://www.gbif.org/dataset/b6349cdd-9d7e-4b23-8c05-a231f0ffa1a0 Catalogue of Life Partnership].
There is only one currently recognised subspecies: ''Diplotaxis tenuifolia'' subsp. ''cretacea'' (Kotov) Sobr.-Vesp., which was described in 1996 and which is restricted to Ukraine and western Russia.<ref>{{cite web |last1=Global Biodiversity Information Facility |title=''Diplotaxis tenuifolia'' subsp. ''cretacea'' (Kotov) Sobr.-Vesp. |url=https://www.gbif.org/species/5376429 |access-date=6 October 2022}}</ref>
''D. tenuifolia'' is assumed to have hybridised with ''D. viminea'' resulting in ''D. muralis.'' <ref>{{Cite journal |last1=Ueno |first1=O. |last2=Wada |first2=Y. |last3=Wakai |first3=M. |last4=Bang |first4=S. W. |date=March 2006 |title=Evidence from Photosynthetic Characteristics for the Hybrid Origin of Diplotaxis muralis from a C 3 ‐C 4 Intermediate and a C 3 Species |url=https://onlinelibrary.wiley.com/doi/10.1055/s-2005-873050 |journal=Plant Biology |language=en |volume=8 |issue=2 |pages=253–259 |doi=10.1055/s-2005-873050 |pmid=16547870 |bibcode=2006PlBio...8..253U |s2cid=260250600 |issn=1435-8603|url-access=subscription }}</ref> It has also been hybridised with ''Raphanus sativus.''<ref>{{Cite journal |doi=10.1104/pp.103.021329 |pmc=167093 |pmid=12857835 |title=Structural and Biochemical Dissection of Photorespiration in Hybrids Differing in Genome Constitution between ''Diplotaxis tenuifolia'' (C3-C4) and Radish (C3) |date=2003 |last1=Ueno |first1=Osamu |last2=Bang |first2=Sang Woo |last3=Wada |first3=Yoshiharu |last4=Kondo |first4=Ayumu |last5=Ishihara |first5=Kuni |last6=Kaneko |first6=Yukio |last7=Matsuzawa |first7=Yasuo |journal=Plant Physiology |volume=132 |issue=3 |pages=1550–1559 }}</ref>
The chromosome number is 2''n'' = 22 (based on British material).<ref name="rich" />
The generic name ''Diplotaxis'' comes from the Ancient Greek, [https://en.wiktionary.org/wiki/%CE%B4%CE%B9%CF%80%CE%BB%CF%8C%CF%82#Greek διπλός (diplos)] = twofold, or double; and [https://en.wiktionary.org/wiki/%CF%84%CE%AC%CF%83%CF%83%CF%89 τάσσω, τάσσειν (tasso, tassein)], which means to put into order, or to draw up in a line (as with troops before a battle). It refers to the double row of seeds in each part of the fruit, which distinguishes this genus from others within the Brassicaceae.<ref name="rich" /> The specific epithet ''tenuifolia'' simply means "narrow-leafed".<ref>{{cite book |last1=Stearn |first1=William T. |title=Botanical Latin: History, Grammar, Syntax, Terminology and Vocabulary |date=1980 |publisher=David & Charles |location=Newton Abbot |isbn=0-7153-5645-3}}</ref>
The common name "rocket" is a corruption of the Italian word ruchetta, which describes various cruciferous plants. This species is also sometimes called wild rocket, sand rocket, Lincoln weed (mainly in Australia) and white rocket; the seeds are sometimes marketed as "wild Italian arugula" or "sylvetta arugula".
==Identification== In Britain it is most likely to be confused with annual wall-rocket, but it does not have a basal rosette, the leaves are divided more than halfway to the midrib, and the fruit has a short stalk (stipe) above the sepal scars.<ref name="Rose" /><ref name="rich" />
The ''Diplotaxis'' species can be separated from most other crucifers by the double row of seeds in each valve of the fruit (although this is a difficult feature to see in unfertilised plants)<ref name="rich" /> and a seedless beak to the silique.<ref name=caruso>{{cite journal |last1=Caruso |first1=G.|last2=Parrella |first2=G. |last3=Giorgini |first3=M. |last4=Nicoletti |first4=R. |title=Crop Systems, Quality and Protection of Diplotaxis tenuifolia |journal=Agriculture |date=2018 |volume=8 |issue=4 |page=55 |doi=10.3390/agriculture8040055|doi-access=free }}</ref> thumb|The short stipe below the fruit is a useful identification feature
== Distribution == It is native to parts of Europe, reaching in the east to Turkey and Syria. It is extinct from Morocco and Algeria, but has been introduced in a number of regions: Cyprus, the Caucasus, the Levant, Yemen, Japan, Australia, New Zealand, New Caledonia, Canada (Ontario, Quebec and Nova Scotia), the United States, Costa Rica, Argentina and Uruguay.<ref name="PoWO">{{cite POWO | id = 1028648-2| title = ''Diplotaxis tenuifolia'' (L.) DC. | accessdate = 17 June 2022}}</ref> thumb|Old walls provide a suitable habitat
Within Europe, its native range covers much of France, the Low Countries, Italy, the Pannonian Basin and the western Balkans up to Macedonia, with generally more thinly scattered populations in northern Greece, Bulgaria, Romania, Crimea, Sicilly, Malta, Sardinia, Corsica and parts of Spain.<ref name="AFE">{{cite book| last1 = Jalas| first1 = J.| last2 = Suominen| first2 = J.| last3 = Lampinen| first3 = R.| year = 1996| title = Atlas Florae Europaeae. Distribution of Vascular Plants in Europe| volume = 11. Cruciferae (Ricotia to Raphanus)| publisher = The Committee for Mapping the Flora of Europe & Societas Biologica Fennica Vanamo| place = Helsinki| isbn=951-9108-11-4| page = 231}}</ref> It has extensively been introduced further north from its native range. In the British Isles the plant is an archaeophyte, with industrial regions and ports still at the centre of the distribution. It is established especially in parts of England and Wales (some believing the plant could even be native to the south-east). Its range has been expanding to the west since the 19th century, but it is still very rare in Scotland and Ireland.<ref>{{cite web| title = Diplotaxis tenuifolia| work = Online Atlas of the British and Irish Flora| url = https://plantatlas.brc.ac.uk/plant/diplotaxis-tenuifolia| access-date = 17 June 2022}}</ref> It has also been introduced into much of Central Europe: throughout Switzerland, Austria, Germany and Poland, with more scattered instances on the southern shores of Norway and Sweden (where it is found in fewer areas that in the recent past), the Baltic States, Belarus and a few locations further east in Ukraine and European Russia. It has also been introduced on Menorca and near Lisbon in Portugal.<ref name="AFE"/>
==Ecology== It is a ruderal plant of roadsides and waste ground.<ref name=rich/><ref name="Flora Iberica"/> It generally grows in places where there is full sunlight and requires moderately damp soils with a slightly alkaline reaction and moderately fertile conditions. It is tolerant of occasional salinity, which allows it to grow on the upper part of beaches and along salt-treated road verges. The Ellenberg values in Britain are L = 8, F = 5, R = 7, N = 6, and S = 1.<ref>{{cite book|last1=Hill|first1=M.O.|last2=Mountford|first2=J.O.|last3=Roy|first3=D.B.|last4=Bunce|first4=R.G.H.|title=Ellenberg's indicator values for British plants. ECOFACT Volume 2. Technical Annex|date=1999|publisher=Institute of Terrestrial Ecology|isbn=1870393481|url=http://nora.nerc.ac.uk/6411/1/ECOFACT2a.pdf|accessdate=29 May 2017}}</ref> In Spain, it can be found at elevations of up to 800{{nbsp}}m.<ref name="Flora Iberica">{{cite book| last = Martínez Laborde| first = J.B.| chapter = Diplotaxis L.| title = Flora iberica| volume = 4. Cruciferae-Monotropaceae| year = 1993| chapter-url = http://www.floraiberica.es/floraiberica/texto/pdfs/04_072_57_Diplotaxis.pdf| page = 349}}</ref> thumb|A likely native habitat is on shingle beaches
There are eleven species of insect that are known to feed on perennial wall-rocket in Britain.<ref name=BRC>{{cite web |last1=Biological Records Centre |title=Insects and their food plants |url=http://dbif.brc.ac.uk/hostsresults.aspx?hostid=1917}}</ref> Five of these are weevils (Curculionidae): *''Ceutorhynchus contractus'' (Marsham), the cabbage leaf weevil - adults feed on leaves and stems *''C. picitarsis'' <small>Gyllenhal</small> - adults feed on leaves and stems *''C. timidus'' <small>Weise</small> (= ''C. chalibaeus'' <small>Germar, 1824</small>) - larvae make galls in the petioles.<ref name=Europe>{{cite web |last1=Plant Parasites of Europe |title=''Ceutorhynchus chalibaeus'' |url=https://bladmineerders.nl/parasites/animalia/arthropoda/insecta/coleoptera/polyphaga/cucujiformia/curculionoidea/curculionidae/conoderinae/ceutorhynchitae/ceutorhynchini/ceutorhynchus/ceutorhynchus-chalibaeus/ |access-date=16 October 2022}}</ref> *''Otiorhynchus ligneus'' - adults need on the roots *''O. ovatus'' - adults feed on the roots.
All five polyphagous and widespread.<ref name="BRC" /><ref>{{cite web |last1=National Biodiversity Network |title=Atlas |url=https://nbnatlas.org/ |access-date=16 October 2022}}</ref>
Four of the phytophagous insects are Diptera (flies). The midge ''Contarinia nasturtii'' <small>(Kieffer)</small> has larvae that infest the stems, leaves and flowerheads, causing distortion and sterility. ''Dasineura brassicae'' <small>(Winnertz)</small> (previously ''D. napi'' <small>(Loew)</small>) is the ''brassica pod midge'', an invasive non-native pest in Britain which causes damage to the developing seedpods. It is particularly of importance on rapeseed crops, but it can also infest wild plants of perennial wall-rocket.<ref>{{cite web |last1=CABI |title=Invasive Species Compendium: ''Dasineura brassicae'' datasheet |url=https://www.cabi.org/isc/datasheet/171969 |access-date=16 October 2022}}</ref> ''Gephyraulus raphanistri'' <small>(Kieffer)</small> is a gall midge that destroys the flowerheads.<ref>{{cite web |last1=Plant Parasites of Europe |title=''Gephyraulus raphanistri'' (Kieffer, 1886) |url=https://bladmineerders.nl/parasites/animalia/arthropoda/insecta/diptera/nematocera/cecidomyiidae/cecidomyiinae/lasiopteridi/oligotrophini/gephyraulus/gephyraulus-raphanistri/ |access-date=16 October 2022}}</ref> None of these species is restricted to wall-rocket and most are quite common, although the [https://species.nbnatlas.org/species/NHMSYS0020470286 NBN Atlas] has no records of brassica pod midge on wild plants in Britain as of 2022.
Finally, three species of Lepidoptera (butterflies and moths) are listed. ''Pieris brassicae'' is the common ''cabbage white'' butterfly, whose larvae eat the leaves and stems of this and many other species of Brassicaceae; ''Evergestis extimalis'' is a micromoth whose larvae feed in the flowerheads; and ''Sitochroa verticalis'' (the ''lesser pearl'') is also a micromoth, the larvae of which are found on a wide variety of plants.
==Uses== Baby leaf rocket is cultivated worldwide as a salad leaf. In addition to ''D. tenuifolia,'' the annual ''Eruca sativa'' is grown and marketed under the same common names. These leaves are usually mixed with other baby leaf crops to form a mesclun-style salad. These crops have become popular due to their distinctive taste and texture in salads.<ref name="caruso" />
Wild rocket is high in ascorbic acid, carotenoids, polyphenols and glucosinolates, such as glucosativin and glucoerucin, which may contribute to the pungent flavour.<ref name=ide/> When the leaves are chewed glucosinolates, through the enzyme myrosinase, are metabolized in isothiocyanates<ref name=foodchem>{{cite journal |vauthors=Spadafora ND, Amaro AL, Pereira MJ, Müller CT, Pintado M, Rogers HJ |date= 15 November 2016 |title=Multi-trait analysis of post-harvest storage in rocket salad (Diplotaxis tenuifolia) links sensorial, volatile and nutritional data |journal=Food Chem |volume=211 |pages=114–123 |doi=10.1016/j.foodchem.2016.04.107 |pmid= 27283614 |url=http://orca.cf.ac.uk/90810/7/Multi-trait-main.pdf |doi-access=free }}</ref> and indoles.<ref name=ide>{{cite journal |vauthors=Bell L, Oruna-Concha MJ, Wagstaff C|date= 1 April 2015|title=Identification and quantification of glucosinolate and flavonol compounds in rocket salad (Eruca sativa, Eruca vesicaria and Diplotaxis tenuifolia) by LC-MS: highlighting the potential for improving nutritional value of rocket crops. |journal=Food Chem |volume=172 |pages=852–861 |doi=10.1016/j.foodchem.2014.09.116 |pmid= 25442630|pmc= 4245720}}</ref> Leaves preserved at 5 °C show a loss of ascorbic acid and glucosinolates, and an increase in polyphenols.<ref name=foodchem/>
One of Trotula's works, ''Treatments for Women'' mentions "wild rocket cooked in wine" in a remedy for sanious flux in women.<ref>{{cite book|last=Green|first=Monica H.|title=The Trotul: an English translation of the medieval compendium of women's medicine|year=2002|publisher=University of Pennsylvania Press|location=Philadelphia|isbn=978-0812218084|page=97|url=https://books.google.com/books?id=yPhNe9ZkcFsC&q=Wild+rocket&pg=PA97}}</ref>
==References== {{Reflist}}
==External links== {{Commons}}
*[http://ucjeps.berkeley.edu/cgi-bin/get_JM_treatment.pl?2240,2422,2424 Jepson Manual Treatment] *[https://plants.usda.gov/java/profile?symbol=DITE4 USDA Plants Profile] *[http://calphotos.berkeley.edu/cgi/img_query?query_src=photos_index&where-taxon=Diplotaxis+tenuifolia ''D. tenuifolia'' photo gallery] – CalPhoto (University of California website) *[https://www.researchgate.net/publication/235344719_Some_Perspectives_on_Rocket_as_a_Vegetable_Crop_A_Review "Some Perspectives on Rocket as a Vegetable Crop: A Review"] – 2012 article in ''Vegetable Crops Research Bulletin'' on ResearchGate.net
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tenuifolia Category:Flora of Western Asia Category:Flora of Europe Category:Edible plants Category:Perennial vegetables