Overview

Comprehensive Description

Description

Unarmed small trees or shrubs. Stipules small, soon deciduous. Leaves alternate or fasciculate, petiolate. Lamina with nerves arranged pinnately. Flowers in an axillary fascicle or solitary. Flowers usually bisexual. Sepals 4-5. Petals 4-5 or 0. Stamens 4-5. Ovary superior, 2-4-locular. Fruit an obovoid fleshy drupe.
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© Mark Hyde, Bart Wursten and Petra Ballings

Source: Flora of Zimbabwe

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Ecology

Associations

Foodplant / false gall
stromatic pseudothecium of Botryosphaeria obtusa causes swelling of branch of Rhamnus

Foodplant / parasite
hypophyllous, effuse colony of Cercospora rhamni parasitises fading leaf of Rhamnus

Foodplant / saprobe
evanescently subiculate pseudothecium of Cucurbitaria rhamni is saprobic on dead branch of Rhamnus

Foodplant / saprobe
clustered, under bark, raising pimples perithecium of Diaporthe fibrosa is saprobic on dead twig of Rhamnus
Remarks: season: 4-6

Foodplant / saprobe
immersed, becoming erumpent conidioma of Dichomera coelomycetous anamorph of Gibberella zeae is saprobic on twig of Rhamnus

Foodplant / saprobe
hysterothecium of Gloniopsis praelonga is saprobic on dead twig of Rhamnus
Remarks: season: 1-12

Foodplant / saprobe
superficial, often in very large clusters pseudothecium of Melanomma pulvis-pyrius is saprobic on dry, hard, decorticate branch wood of Rhamnus
Remarks: season: 9-5

Foodplant / saprobe
colony of Gonytrichum dematiaceous anamorph of Melanopsammella inaequalis is saprobic on fallen, dead branch of Rhamnus
Remarks: season: 1-12

Foodplant / saprobe
stromatic, superficial, grouped perithecium of Nectria punicea is saprobic on dead branch of Rhamnus
Remarks: season: 2

Foodplant / parasite
mostly hypophyllous pycnium of Puccinia coronata parasitises live leaf of Rhamnus

Foodplant / saprobe
sporodochium of Sarcopodium anamorph of Sarcopodium tortuosum is saprobic on dead wood of Rhamnus

Foodplant / saprobe
fruitbody of Trametes gibbosa is saprobic on dead, fallen, decayed wood of Rhamnus
Other: minor host/prey

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
                                        
Specimen Records:100Public Records:35
Specimens with Sequences:89Public Species:8
Specimens with Barcodes:87Public BINs:0
Species:17         
Species With Barcodes:15         
          
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Source: Barcode of Life Data Systems (BOLD)

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Barcode data

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Source: Barcode of Life Data Systems (BOLD)

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Locations of barcode samples

Collection Sites: world map showing specimen collection locations for Rhamnus

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Wikipedia

Rhamnus (genus)

"Buckthorn" redirects here. For other plants of that name, see List of plants named Buckthorn.

Rhamnus is a genus of about 150 species (fewer, if some species are placed in Frangula), which are shrubs or small trees, commonly known as buckthorns. It is part of the family Rhamnaceae. Its species range from 1 to 10 meters tall (rarely to 15 m) and are native mainly in east Asia and North America, but found throughout the temperate and subtropical Northern Hemisphere, and also more locally in the subtropical Southern Hemisphere in parts of Africa and South America.

Both deciduous and evergreen species occur. The leaves are simple, 3 to 15 centimeters long, and arranged either alternately or in opposite pairs. One distinctive character of many buckthorns is the way the veination curves upward towards the tip of the leaf. The plant bears fruits which are black or red berry-like drupe. The name is due to the woody spine on the end of each twig in many species.

Description[edit]

Rhamnus species are shrubs or small to medium-sized trees, with deciduous or rarely evergreen foliage. Branches are unarmed or end in a woody spine. Leaves opposite or alternately arraigned, a few species have clusters of leaves arising from the same point on short shoots. The leaf blades are undivided and pinnately veined. Leaf margins are serrate or rarely entire. Most species have yellowish green, small, bisexual or unisexual, rarely polygamous flowers; which are produced singly or in axillary cymes, cymose racemes, or cymose panicles containing a few flowers. Calyx tube campanulate to cup-shaped, with 4 or 5 ovate-triangular sepals, which are adaxially ± distinctly keeled. Petals 4 or 5 but a few species may lack petals. The petals are shorter than the sepals. Flowers have 4 or 5 stamens which are surrounded by and equal in length the petals or are shorter. The anthers are dorsifixed. The superior ovary is free, rounded, with 2-4 chambers. Fruits are a 2-4 stoned, berrylike drupe, which is obovoid-globose or globose shaped. Seeds are obovoid or oblong-obovoid shaped, unfurrowed or abaxially or laterally margined with a long, narrow, furrow. The seeds have fleshy endosperm.[1]

Distribution[edit]

Rhamnus has a nearly cosmopolitan distribution,[2] with about 150 species which are native from temperate to tropical regions, the majority of species are from east Asia and North America, with a few species in Europe and Africa.[1]

North American species include alder-leaf buckthorn (R. alnifolia) occurring across the continent, Carolina buckthorn (R. (F.) caroliniana) in the east, cascara buckthorn (R. (F.) purshiana) in the west, and the evergreen California buckthorn or coffeeberry (R. (F.) californica) and hollyleaf buckthorn (R. crocea), also in the west.

In South America, Rhamnus diffusus is a small shrub native to the Valdivian temperate rain forests of Chile.

Buckthorns may be confused with dogwoods, which share the curved leaf venation; indeed, "dogwood" is a local name for R. prinoides in southern Africa. The two plants are easy to distinguish by slowly pulling a leaf apart; dogwoods will exude thin, white latex strings, while buckthorns will not.

Classification[edit]

The genus is divided into two subgenera, sometimes treated as separate genera:

  • Subgenus Rhamnus: flowers with four petals, buds with bud scales, leaves opposite or alternate, branches with spines. Species include:
19th century illustration of Rhamnus frangula

Ecology[edit]

Some species are invasive outside their natural ranges. R. cathartica was introduced into the United States as a garden shrub and has become an invasive species in many areas there. It is a primary host of the soybean aphid (Aphis glycines), a pest for soybean farmers across the US. The aphids use the buckthorn as a host for the winter and then spread to nearby soybean fields in the spring.[3] Italian buckthorn (R. alaternus), an evergreen species from the Mediterranean region, has become a serious weed in some parts of New Zealand,[4] especially on Hauraki Gulf islands.

Buckthorns are used as food plants by the larvae of many Lepidoptera species.

Uses[edit]

The fruit of most species contain a yellow dye and the seeds are rich in protein. Oils from the seeds are used for making lubricating oil, printing ink, and soap.[1]

Some species may cause demyelinating polyneuropathies.[5] The purging buckthorn (R. cathartica) is a widespread European native species used in the past as a purgative, though its toxicity makes this a very risky herbal medicine and it is no longer in use.

Another European species, alder buckthorn (R. frangula syn. Frangula alnus) was of major military importance in the 15th to 19th centuries, as its wood provided the best quality charcoal for gunpowder manufacture.[6]

Many species have been used to make dyes. R. purshianus bark and fruit yield a yellow dye and, when mixed with alum, a green dye that has been used in art.[7] R. utilis provides china green, a dye used to give a bright green color to silk and wool.[8] Another species, Avignon buckthorn (R. saxatilis) provides the yellow dye Persian berry, made from the fruit.

R. prinoides is known as gesho in Ethiopia, where it is used to make a mead called tej.

References[edit]

  1. ^ a b c "Rhamnus in Flora of China @". Efloras.org. Retrieved 2013-05-07. 
  2. ^ "Rhamnus in Flora of Pakistan @". Efloras.org. Retrieved 2013-05-07. 
  3. ^ Box: 2207A (2012-04-03). "SDSU Department of Plant Science: Managing Soybean Aphids". Sdstate.edu. Retrieved 2013-05-07. 
  4. ^ Synergy International Limited <http://www.synergy.co.nz> (2006-03-23). "issg Database: Ecology of Rhamnus alaternus". Issg.org. Retrieved 2013-05-07. 
  5. ^ "Peripheral Neuropathy: Peripheral Nervous System and Motor Unit Disorders: Merck Manual Professional". Merckmanuals.com. Retrieved 2013-05-07. 
  6. ^ Francis Montagu Smith (1871). A handbook of the manufacture and proof of gunpowder, as carried on at the Royal Gunpowder Factory, Waltham Abbey. H.M. Stationery Office. pp. 26–. Retrieved 2 April 2013. 
  7. ^ Mozingo, H. N. Shrubs of the Great Basin: A Natural History. Reno, Nevada: University of Nevada Press. 1987. 342 p. In: Habeck, R. J. 1992. Rhamnus purshiana. Fire Effects Information System. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
  8. ^ Brunello, F. The Art of Dyeing in the History of Mankind. AATCC. 1973. pg. 381.
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