Juglans regia

Juglans regia
Mature Walnut Tree
Conservation status
Near Threatened (IUCN 3.1)
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Fagales
Family:	Juglandaceae
Genus:	Juglans
Species:	J. regia
Binomial name
Juglans regia L.
Synonyms
Juglans duclouxiana Dode J. fallax Dode J. kamaonia (C. de Candolle) Dode J. orientis Dode J. regia var. sinensis C. de Candolle J. sinensis (C. de Candolle) Dode

Juglans regia, the Persian walnut, English walnut, or especially in Great Britain, Common walnut, is an Old World walnut tree species native to the region stretching from the Balkans eastward to the Himalayas and southwest China. The largest forests are in Kyrgyzstan, where trees occur in extensive, nearly pure walnut forests at 1,000–2,000 m altitude (Hemery 1998)—notably at Arslanbob in Jalal-Abad Province.

Description

Juglans regia is a large deciduous tree attaining heights of 25–35 m, and a trunk up to 2 m diameter, commonly with a short trunk and broad crown, though taller and narrower in dense forest competition. It is a light-demanding species, requiring full sun to grow well.

The bark is smooth, olive-brown when young and silvery-grey on older branches, and features scattered broad fissures with a rougher texture. Like all walnuts, the pith of the twigs contains air spaces; This chambered pith is brownish in color. The leaves are alternately arranged, 25–40 cm long, odd-pinnate with 5–9 leaflets, paired alternately with one terminal leaflet. The largest leaflets the three at the apex, 10–18 cm long and 6–8 cm broad; the basal pair of leaflets much smaller, 5–8 cm long, the margins of the leaflets entire. The male flowers are in drooping catkins 5–10 cm long, and the female flowers terminal, in clusters of two to five, ripening in the autumn into a fruit with a green, semi-fleshy husk and a brown corrugated nut. The whole fruit, including the husk, falls in autumn; the seed is large, with a relatively thin shell, and edible, with a rich flavor.

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  Taxonomic keys

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  Male flower

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  Female flower

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  Fruit

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  Seed

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  Bark

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  Foliage

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  Habit

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  Walnuts from northern Poland

• 4 walnut kernels.JPG

  Close-up of the kernels of a walnut

Taxonomy

The word 'walnut' derives from the Germanic wal- and Old English wealhhnutu, literally "foreign nut", wealh meaning "foreign" (wealh is akin to the terms Welsh and Vlach; see Walha and History of the term Vlach).^[1] For the walnut to be identified as a "foreign" nut by Anglo-Saxons arriving in the fifth century, native Britons must have passed to them the tradition that it had been introduced to England from Gaul and Italy. The Latin name for the walnut was nux Gallica, "Gallic nut";^[1] the Gaulish region of Galatia in Anatolia lies in highlands at the western end of the tree's presumed natural distribution.

Walnut does not distinguish the tree from other species of Juglans. Other names include Common Walnut in Britain; Persian Walnut in South Africa^[2] and Australia;^[3] and English Walnut in North America, Great Britain,^[4] New Zealand,^[5] and Australia,^[3] the latter name possibly because English sailors were prominent in Juglans regia nut distribution at one time.^[6] Alternatively, Walter Fox Allen stated in his 1912 treatise What You Need to Know About Planting, Cultivating and Harvesting this Most Delicious of Nuts:^[7] "In America it has commonly been known as English Walnut to distinguish it from our native species."

In the Chinese language, the edible, cultivated walnut is called 胡桃 (hú táo in Mandarin), which means literally "Hu peach", suggesting that the ancient Chinese associated the introduction of the tree into East Asia with the Hu barbarians of the regions north and northwest of China. In Mexico, it is called nogal de Castilla,^[8] suggesting that the Mexicans associate the introduction of the tree into Mexico with Spaniards from Castile.

Cultivars

J. regia 'Buccaneer' Produces an abundant crop of seeds. A self-fertile cultivar, it produces pollen over a long period and is thus a valuable pollinator for other cultivars. The tree is about the same size as a seedling walnut, it comes into leaf very late and so usually avoids damage by late frosts.

The Old English term "wealhhnutu" is a late book-name (Old English Vocabularies, Wright & Wulker) therefore the remark that the Anglo-Saxons inherited the Walnut tree from the Romans does not follow from this name.

Distribution and habitat

J. regia is native to the mountain ranges of Central Asia, extending from Xinjiang province of western China, parts of Kazakhstan, Uzbekistan and southern Kirghizia and from lower ranges of mountains in Nepal, Bhutan, Tibet, northern India and Pakistan, through Afghanistan, Turkmenistan and Iran to portions of Azerbaijan, Armenia, Georgia and eastern Turkey. In these countries, there is a great genetic variability, in particular ancestral forms with lateral fruiting. During its migration to western Europe, the common walnut lost this character by natural selection on account of competition with other vigorous forest species such as oaks. They became big trees with terminal fruiting. A small remnant population of these J. regia trees have survived the last glacial period in Southern Europe, but the bulk of the wild germplasm found in the Balkan peninsula and much of Turkey was most likely introduced from eastern Turkey by commerce and settlement several thousand years ago.

In the fourth century BC, Alexander the Great introduced this "Persian nut" (Theophrastus' καρυα ή Περσική^[9]) in Macedonia and Greece ancestral forms with lateral fruiting from Iran and Central Asia. They hybridized with terminal-bearing forms to give lateral bearing trees. These lateral bearers were spread in southern Europe and northern Africa by Romans. Recent prospections in walnut populations of the Mediterrean Basin allowed to select interesting trees of this type. In the Middle Ages, the lateral bearing character was introduced again in southern Turkey by merchants traveling along the Silk Road. J. regia germplasm in China is thought to have been introduced from Central Asia about 2 000 years ago, and in some areas has become naturalized. Cultivated distribution now includes North and South America (Chile, Argentine), Australia, New Zealand, South Africa and Japan. So, the Persian walnut is grown from 30 to 50 degrees of latitude in the Northern hemisphere and from 30 to 40 degrees in the Southern hemisphere.

The walnut was introduced into western and northern Europe very early, by Roman times or earlier, and to the Americas by the 17th century, by English colonists. Important nut-growing regions include France, Serbia, Greece, Bulgaria, and Romania in Europe, China in Asia, California in North America, and Chile in South America. Lately the crop has spread to other regions: New Zealand and the southeast of Australia.^[10] It is cultivated extensively for its high-quality nuts, eaten both fresh and pressed for their richly flavored oil; numerous cultivars have been selected for larger nuts with thinner shells.

Ecology

The Life Cycle:

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  Buds

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  Young tree

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  Fertilized flowers

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  Mature tree

Nutritional value

Walnut, english

Persian walnut, Juglans regia
Nutritional value per serving
Serving size	100 grams
Energy	2,738 kJ (654 kcal)
Carbohydrates	13.71
- Starch	0.06
- Sugars	2.61
- Lactose	0
- Dietary fiber	6.7
Fat	65.21
- saturated	6.126
- monounsaturated	8.933
- polyunsaturated	47.174
Protein	15.23
Water	4.07
Alcohol	0
Caffeine	0
Vitamin A equiv.	1 μg (0%)
Vitamin A	20 IU
- beta-carotene	12 μg (0%)
- lutein and zeaxanthin	9 μg
Thiamine (vit. B1)	0.341 mg (30%)
Riboflavin (vit. B2)	0.15 mg (13%)
Niacin (vit. B3)	1.125 mg (8%)
Pantothenic acid (B5)	0.570 mg (11%)
Vitamin B6	0.537 mg (41%)
Folate (vit. B9)	98 μg (25%)
Vitamin B12	0 μg (0%)
Vitamin C	1.3 mg (2%)
Vitamin D	0 μg (0%)
Vitamin D	0 IU (0%)
Vitamin E	0.7 mg (5%)
Vitamin K	2.7 μg (3%)
Calcium	98 mg (10%)
Iron	2.91 mg (22%)
Magnesium	158 mg (45%)
Manganese	3.414 mg (163%)
Phosphorus	346 mg (49%)
Potassium	441 mg (9%)
Sodium	2 mg (0%)
Zinc	3.09 mg (33%)
Percentages are relative to US recommendations for adults. Source: USDA Nutrient Database

A study of ten cultivars of J. regia in Turkey showed significant variations in fatty acid content:^[11]

• 62% - 71% fat
  • saturated fat (as a percentage of total fatty acid):
    • 5.2% - 7.3% palmitate
    • 2.6% - 3.7% stearate
  • unsaturated fat (as a percentage of total fatty acid):
    • 21.2% - 40.2% oleate (monounsaturated)
    • 43.9% - 60.1% linoleate (diunsaturated)
    • 6.9% - 11.5% linolenate (triunsaturated)

Potential biological effects

Walnuts and other tree nuts are important food-allergen sources that have the potential to be associated with life-threatening, IgE-mediated systemic reactions in some individuals.^[12][13]

The extracts of walnuts have antioxidant and antiproliferative activity due to a high phenolic content.^[14]

In vitro tests of walnut extract has shown a high anti-atherogenic potential and osteoblastic activity suggesting a potential beneficial effect of a walnut-enriched diet on cardioprotection and bone loss.^[15]

The extract from walnut leaves is an antioxidant, decreases the blood sugar level and has a positive impact on lipid metabolism. The extract suppresses functional insufficiency of liver links synthethising enzymes, increases the antitoxic action of hepatocytes and improves the functional insufficiency of kidneys.^[16] The ethanolic extract from leaves of J. regia has an antidiabetic effect on diabetes-induced rats.^[17]

Bark and leaf crude extracts of Juglans regia ,and Juglans mollis , showed in vitro anti-Mycobacterium tuberculosis activity.^[18]

Culture

In Skopelos, a Greek island in the Aegean Sea, local legend suggests that whoever plants a walnut tree will die as soon as the tree can "see" the sea. This has not been proven as fact; however, it might take some time to find a local arborist willing to take on the job of planting a walnut tree. Most planting is done by field rats (subfamily Murinae). In Flanders, a folk saying states: "By the time the tree is big, the planter sure will be dead" (Dutch: Boompje groot, plantertje dood). This saying refers to the relatively slow growth rate of the tree.

Cultivation

Walnut trees grow best in rich, deep soil with full sun and long summers, such as the California central valley. In the U.S., Juglans regia is often grafted onto a rootstock of native Black Walnut, Juglans hindsii to provide disease resistance. Other plants often will not grow under walnut trees because the fallen leaves and husks contain Juglone, a dark brown chemical which acts as a natural herbicide. Horses should not eat walnut leaves or they may develop laminitis, a hoof ailment. Mature trees may reach 50 feet in height and width, and live more than 200 years, developing massive trunks more than eight feet thick.

Other Uses

Walnut heartwood is a heavy, hard, open-grained hardwood. Freshly cut live wood may be Dijon-mustard color, darkening to brown over 1-3 days. The dried lumber is a rich chocolate-brown to black, with cream to tan sapwood and may feature unusual figure such as "curly," "bee's wing," "bird's eye" and "rat tail," among others. It is prized by fine woodworkers for its durability, luster and chatoyance and is used for high-end flooring, guitars, furniture, veneers, knobs and handles.

American pioneers used juglone from ground walnut husks and leaves to make a deep brown ink, paints and wood stains.

Green husk extracts of walnut have insecticidal properties. It killed 98% of Tetranychus cinnabarinus (Spider mite)^[19]

See also

Food portal

• Black walnut
• Taxonomy of walnut tree varieties

Notes

1. ^ ^{a b} Online Etymology Dictionary - "Walnut"
2. ^ L.C. van Zyl "Grafting of Walnut (Juglans regia L.) with Hot Callusing Techniques Under South African Conditions", University of the Free State, 2009 http://etd.uovs.ac.za/ETD-db//theses/available/etd-09172009-160603/unrestricted/VanZylLC.pdf
3. ^ ^{a b} http://www.austnuts.com.au/walnuts.html
4. ^ D.S. Hill, Skegness, Lincs, United Kingdom: Pests of Crops in Warmer Climates and Their Control p.651, Springer Science+Business Media, 2008
5. ^ http://www.nzplantpics.com/not_nz_trees.htm
6. ^ "?". http://www.agmrc.org/agmrc/commodity/nuts/englishwalnut/englishwalnutsprofile.htm. ^{[dead link]}
7. ^ "?". http://walnutsweb.com/walnuts/How+to+Grow+English+Walnuts. ^{[dead link]}
8. ^ Juglans Regia (Spanish)
9. ^ Theophrastus, Enquiry into Plants III.6.2, III.14.4
10. ^ "FAO corporate document repository: Walnut". http://www.fao.org/docrep/007/y5704e/y5704e03.htm. 
11. ^ Ozkhan, Gulcan; Koyuncu, M. Ali (2005). "Physical and chemical composition of some walnut ( Juglans regia L) genotypes grown in Turkey" (free). Grasas y Aceites (Consejo Superior de Investigaciones Científicas) 56 (2): 141–146. doi:10.3989/gya.2005.v56.i2.122. 
12. ^ Suzanne S. Teuber, Koren C. Jarvis, Abhaya M. Dandekar, W.Rich Peterson, Aftab A. Ansari "Identification and cloning of a complementary DNA encoding a vicilin-like proprotein, Jug r 2, from English walnut kernel (Juglans regia), a major food allergen" The Journal of Allergy and Clinical Immunology - December 1999 (Vol. 104, Issue 6, Pages 1311-1320)
13. ^ http://foodallergens.ifr.ac.uk/food.lasso?selected_food=53
14. ^ Negi AS, Luqman S, Srivastava S, Krishna V, Gupta N, Darokar MP" Antiproliferative and antioxidant activities of Juglans regia fruit extracts." Pharm Biol. 2011 Jun;49(6):669-73
15. ^ Papoutsi Z, Kassi E, Chinou I, Halabalaki M, Skaltsounis LA, Moutsatsou P "Walnut extract (Juglans regia L.) and its component ellagic acid exhibit anti-inflammatory activity in human aorta endothelial cells and osteoblastic activity in the cell line KS483." Br J Nutr. 2008 Apr;99(4):715-22
16. ^ Authors: Dzhafarova RE, Garaev GSh, Dzhafarkulieva ZS"Antidiabetic action of extract of Juglans regia L" Georgian Med News. 2009 May;(170):110-4
17. ^ Asgary S, Parkhideh S, Solhpour A, Madani H, Mahzouni P, Rahimi P.,"Effect of Ethanolic Extract of Juglans regia L. on Blood Sugar in Diabetes-Induced Rats." J Med Food. 2008 Sep;11(3):533-8
18. ^ Cruz-Vega DE, Verde-Star MJ, Salinas-González N, Rosales-Hernández B, Estrada-García I, Mendez-Aragón P, Carranza-Rosales P, González-Garza MT, Castro-Garza J"Antimycobacterial activity of Juglans regia, Juglans mollis, Carya illinoensis and Bocconia frutescens." Phytother Res. 2008 Mar 13;
19. ^ Wang YN, Wang HX, Shen ZJ, Zhao LL, Clarke SR, Sun JH, Du YY, Shi GL"Methyl palmitate, an acaricidal compound occurring in green walnut husks". J Econ Entomol. 2009 Feb;102(1):196-202

References

• Flora Europaea: Juglans regia
• Flora of Pakistan: Juglans regia
• Chauhan, N., Wang, K.C., Wegiel, J. and Malik, M.N. (2004) "Walnut Extract Inhibits the Fibrillization of Amyloid Beta-Protein, and also Defibrillizes its Preformed Fibrils", Current Alzheimer Research, 1 (3), p. 183–188
• Cortés, B., Núñez, I., Cofán, M., Gilabert, R., Pérez-Heras, A., Casals, E., Deulofeu, R. and Ros, E. (2006) "Acute Effects of High-Fat Meals Enriched With Walnuts or Olive Oil on Postprandial Endothelial Function", J. Am. Coll. Cardiol., 48 (October), p. 1666–1671, doi:10.1016/j.jacc.2006.06.057
• Hemery, G. E. (1998). Walnut seed-collecting expedition to Kyrgyzstan in Central Asia. Quarterly Journal of Forestry 92 (2): 153-157.
• Society for Neuroscience (2007). "News Release: Diet of walnuts, blueberries improve cognition; may help maintain brain function", Society for Neuroscience, 5 November 2007
• eFloras, Missouri Botanical Garden & Harvard University Herbaria (FOC Vol. 4 Page 282). "Juglans regia". http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200006112. Retrieved 2009. 

External links

External identifiers for Juglans regia
EOL	487229
ITIS	503244
NCBI	51240
Also found in: Wikispecies