Humulus lupulus

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Contents

Common hop
Hopfen1.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Rosales
Family: Cannabaceae
Genus: Humulus
Species:
H. lupulus
Binomial name
Humulus lupulus
L.
Synonyms [1]
  • Humulus cordifoliusMiq.
  • Humulus volubilisSalisb. nom. illeg.
  • Humulus vulgarisGilib.
  • Lupulus amarusGilib.
  • Lupulus communisGaertn.
  • Lupulus humulusMill.
  • Lupulus scandensLam. nom. illeg.
male inflorescences Humulus lupulus male flowers RF.jpg
male inflorescences

Humulus lupulus, the common hop or hops, is a species of flowering plant in the hemp family Cannabaceae, native to West Asia, Europe and North America. It is a perennial, herbaceous climbing plant which sends up new shoots in early spring and dies back to a cold-hardy rhizome in autumn. [2] It is dioecious (having separate male and female plants).

As the female cone-shaped flowers (hops) are used to preserve and flavor beer, the species is widely cultivated for the brewing industry. [2]

Description

Humulus lupulus is a perennial herbaceous plant up to 10 metres (33 feet) tall, living up to 20 years. [3] It has simple leaves with 3–5 deep lobes that can be opposite or alternate. [4] The species is triggered by the longer summer days to flower, [5] usually around July or August in the Northern Hemisphere. [6] The plant is dioecious, with male and female flowers on separate plants. The fragrant flowers are wind-pollinated. [7] The staminate (male) flowers do not have petals, while the pistillate (female) flowers have petals enveloping the fruit. The female flower cones (or strobili) are known as hops. [3] The fruit is an achene, meaning that it is dry and does not split open at maturity. [4] The achene is surrounded by tepals and lupulin-secreting glands are concentrated on the fruit. [8] [9]

The species is sometimes described as a bine rather than a vine because it has stiff downward facing hairs that provide stability and allow it to climb. [3]

Chemistry

H. lupulus contains myrcene, humulene, xanthohumol, myrcenol, linalool, tannins, and resin.

Hops are unique for containing secondary metabolites, flavonoids, oils, and polyphenols that impact the flavor of the products they are common in, such as beer. [10] The bitter flavors in hops can be accounted for by acids composed of prenylated polyketides (a group of secondary metabolites), which highly impact the taste of hop-based products. [11] Multiple genes have been identified as factors in the expression of taste including O-methyltransferase 1, geranyl diphosphate synthase, and chalcone synthase. Genomic analyses have shown evidence that the intervention of humans in the selection process of the hop over the thousands of years it has been cultivated have provided noticeable enhancements in aroma and bitterness as well as selection of varieties with high yield rates. [12]

Flowering, growth, and stress response

Predicted genes in homologous primary contigs have been identified as accounting for various traits expressed via variation in the growth, flowering, and stress responses in the plant. These homologous primary contigs correspond to regions with large amounts of sequence variation. Genes in the hop that contain higher rates of sequence divergence in homologous primary contigs (overlapping DNA sequences inherited by a common ancestor) have been attributed to the expression of flowering, growth and responses to (both abiotic and biotic) stress in the plant. The responses to stress are thought to manifest in the distinct differences and difficulties in the cultivation processes between geographically popular varieties of the hop plant. [13] Outside environmental stress, such as changes in temperature and water availability has also been shown to significantly alter the transcriptome and incite reductions in genes known to be involved in the synthesis of secondary metabolites (including bitter acids), which are organic compounds produced that do not impact development or reproduction of hops. Environmental stress has also been shown to reduce expression of the valerophenone synthase gene, which is known to be an essential genetic component in the regulation of bitter acid production. This shows that impacts of outside stress on H. lupulus likely has a direct implication of the expression of the bitter flavor that remains an essential component of the popularity of the plant. [10]

Research

  • Humulus lupulus contains xanthohumol, which is converted by large intestine bacteria into the phytoestrogen 8-prenylnaringenin, which may have a relative binding affinity to estrogen receptors [14] as well as potentiating effects on GABAA receptor activity [15]
  • Humulus lupulus extract is antimicrobial, an activity which has been exploited in the manufacture of natural deodorant. [16]
  • Spent H. lupulus extract has also been shown to have antimicrobial and anti-biofilm activities, raising the possibility this waste product of the brewing industry could be developed for medical applications. [17]
  • Extracts of the bitter alpha-acids present in H. lupulus have been shown to decrease nocturnal activity, acting as a sleep aide, in certain concentrations. [18]

Because of the growing understanding regarding the hop's overlap in gene structures with cannabidiolic acid synthase, the precursor structure to cannabidiol, there is a gap in general understanding about potential unknown compounds and benefits in hops. As the understanding of the health benefits available in cannabidiol increases, there is a growing demand to further investigate the overlap between cannabidiolic acid synthase and H. lupulus. [19]

Limitations

The genome of H. lupulus is relatively large and has been shown to be a similar size to the human genome. The complexity of the hop genome has made it difficult to understand and identify unknown genetic properties, however with the growing availability of accessible sequencing, there is room for more advanced understanding of the plant. [19] Because of the growing concern of climate change, and the assumption that there will be an increase of heat waves, it is likely that growing large yields of hops could become more difficult. This could result in changes to the transcriptome of the hop, or result in a decrease of certain varieties, leaving less room for further research. [10]

Taxonomy

Relation to Cannabis sativa

The hop is within the same family of plants such as hemp and marijuana, called Cannabaceae. [13] The hop plant diverged from Cannabis sativa over 20 million years ago and has evolved to be three times the physical size. [20] [21] [12] [22] The hop and C. sativa are estimated to have approximately a 73% overlap in genomic content. [23] The overlap between enzymes includes polyketide synthases and prenyltransferases. [24] The hop and C. sativa also have significant overlap in the cannabidiolic acid synthase gene, which is expressed in the tissues of the leaves in both plants. [13]

Varieties

Cultivation of hops in Ystad 2017 Humle (Humulus lupulus)-2017-Ystad.jpg
Cultivation of hops in Ystad 2017
'Golden' hop Humulus lupulus 'Aurea' - Golden Hop.jpg
'Golden' hop

The five varieties of this species (Humulus lupulus) are:

Many cultivars are found in the list of hop varieties. A yellow-leafed ornamental cultivar, Humulus lupulus 'Aureus', is cultivated for garden use. It is also known as golden hop, and holds the Royal Horticultural Society's Award of Garden Merit (AGM). [28] [29]

Etymology

The genus name Humulus is a medieval name that was at some point Latinized after being borrowed from a Germanic source exhibiting the h•m•l consonant cluster, as in Middle Low German homele.

According to Soviet Iranist V. Abaev this could be a word of Sarmatian origin which is present in the modern Ossetian language (Ossetian : Хуымæллæг) and derives from proto-Iranian hauma-arayka, an Aryan haoma . [30]

From Sarmatian dialects this word spread across Eurasia, thus creating a group of related words in Turkic, Finno-Ugric, Slavic and Germanic languages (see Russian : хмель, Chuvash хăмла, Finnish humala, Hungarian komló, Mordovian комла, Avar хомеллег).

The specific epithet lupulus is Latin for "small wolf". [31] The name refers to the plant's tendency to strangle other plants, mainly osiers or basket willows (Salix viminalis), like a wolf does a sheep. [3] Hops could be seen growing over these willows so often that it was named the willow-wolf. [31]

The English word hop is derived from the Middle Dutch word hoppe, also meaning Humulus lupulus. [32]

Distribution and habitat

The plant is native to Europe, western Asia and North America. [31]

It grows best in the latitude range of 38°–51° in full sun with moderate amounts of rainfall. [2]

Ecology

The flowers attract butterflies, [31] amongst other insects.

Animal pests

Diseases

Toxicity

H. lupulus can cause dermatitis to some who handle them. It is estimated that about 1 in 30 people are affected by this. [9]

Uses

H. lupulus is first mentioned in 768 CE when King Pepin donated hops to a monastery in Paris. Cultivation was first recorded in 859 CE, in documents from a monastery in Freising, Germany. [33]

The chemical compounds found in H. lupulus are the main components in flavoring and bittering beer. The fragrant flower cones, known as hops, impart a bitter flavor and also have aromatic and preservative qualities. [34] Some other compounds help with creating foam in beer. Chemicals such as linalool and aldehydes contribute to the flavor of beer. The main components of bitterness in beer are iso-alpha acids, with many other compounds contributing to beer's overall bitterness. [35] Until the Middle Ages, many varieties of plant were used to flavor beer, including most commonly Myrica gale . [33] H. lupulus became favored because it contains preserving agents which prolong the viability of a brew.

Culture

H. lupulus was voted the county flower of Kent in 2002 following a poll by the wild flora conservation charity Plantlife. [36]

Related Research Articles

<span class="mw-page-title-main">Hops</span> Flower used to flavour beer and other beverages

Hops are the flowers of the hop plant Humulus lupulus, a member of the Cannabaceae family of flowering plants. They are used primarily as a bittering, flavouring, and stability agent in beer, to which, in addition to bitterness, they impart floral, fruity, or citrus flavours and aromas. Hops are also used for various purposes in other beverages and herbal medicine. The hops plants have separate female and male plants, and only female plants are used for commercial production. The hop plant is a vigorous, climbing, herbaceous perennial, usually trained to grow up strings in a field called a hopfield, hop garden, or hop yard when grown commercially. Many different varieties of hops are grown by farmers around the world, with different types used for particular styles of beer.

<i>Cannabis</i> Genus of flowering plants

Cannabis is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: Cannabis sativa, C. indica, and C. ruderalis. Alternatively, C. ruderalis may be included within C. sativa, all three may be treated as subspecies of C. sativa, or C. sativa may be accepted as a single undivided species. The genus is widely accepted as being indigenous to and originating from Asia.

<i>Humulus</i> Genus of flowering plants belonging to the hemp and hackberry family

Humulus, or hop, is a small genus of flowering plants in the family Cannabaceae. The hop is native to temperate regions of the Northern Hemisphere. Hops are the female flowers of the hop species H. lupulus; as a main flavor and aroma ingredient in many beer styles, H. lupulus is widely cultivated for use by the brewing industry.

<i>Cannabis sativa</i> Plant species

Cannabis sativa is an annual herbaceous flowering plant. The species was first classified by Carl Linnaeus in 1753. The specific epithet sativa means 'cultivated'. Indigenous to Eastern Asia, the plant is now of cosmopolitan distribution due to widespread cultivation. It has been cultivated throughout recorded history and used as a source of industrial fiber, seed oil, food, and medicine. It is also used as a recreation drug and for religious and spiritual purposes.

<span class="mw-page-title-main">Linalool</span> Chemical compound with a floral aroma

Linalool refers to two enantiomers of a naturally occurring terpene alcohol found in many flowers and spice plants. Linalool has multiple commercial applications, the majority of which are based on its pleasant scent. A colorless oil, linalool is classified as an acyclic monoterpenoid. In plants, it is a metabolite, a volatile oil component, an antimicrobial agent, and an aroma compound. Linalool has uses in manufacturing of soaps, fragrances, food additives as flavors, household products, and insecticides. Esters of linalool are referred to as linalyl, e.g. linalyl pyrophosphate, an isomer of geranyl pyrophosphate.

<span class="mw-page-title-main">Myrcene</span> Chemical compound

Myrcene, or β-myrcene, is a monoterpene. A colorless oil, it occurs widely in essential oils. It is produced mainly semi-synthetically from Myrcia, from which it gets its name. It is an intermediate in the production of several fragrances. α-Myrcene is the name for the isomer 2-methyl-6-methylene-1,7-octadiene, which has not been found in nature.

<span class="mw-page-title-main">Humulene</span> Chemical compound

Humulene, also known as α-humulene or α-caryophyllene, is a naturally occurring monocyclic sesquiterpene (C15H24), containing an 11-membered ring and consisting of 3 isoprene units containing three nonconjugated C=C double bonds, two of them being triply substituted and one being doubly substituted. It was first found in the essential oils of Humulus lupulus (hops), from which it derives its name. Humulene is an isomer of β-caryophyllene, and the two are often found together as a mixture in many aromatic plants.

β-Pinene Chemical compound

β-Pinene is a monoterpene, an organic compound found in plants. It is one of the two isomers of pinene, the other being α-pinene. It is a colorless liquid soluble in alcohol, but not water. It has a woody-green pine-like smell.

<i>Humulus japonicus</i> Species of flowering plant

Humulus japonicus, known as Japanese hops, is an ornamental plant in the family Cannabaceae. Some authorities have it as a synonym of Humulus scandens.

Hop latent viroid is a viroid, which is known to cause the Dudding Disease in hemp and cannabis. It is a non-capsulated strand of RNA and an obligate parasite that requires the presence of a compatible host for its survivability. It can have minor effects on hop quality, but has shown to cause severe stunting in hemp and cannabis. Due to its ability to remain undetected, it has become an issue of significant risk for some hemp and cannabis cultivars. Studies regarding this viroid and its ability to infiltrate its plant host are well underway; however, addressing measures to reduce its introduction into growing environments is still challenging.

<span class="mw-page-title-main">Cannabaceae</span> Family of flowering plants comprising hops, hemps, and hackberries

Cannabaceae is a small family of flowering plants, known as the hemp family. As now circumscribed, the family includes about 170 species grouped in about 11 genera, including Cannabis (hemp), Humulus (hops) and Celtis (hackberries). Celtis is by far the largest genus, containing about 100 species.

<span class="mw-page-title-main">Xanthohumol</span> Chemical compound

Xanthohumol is a natural product found in the female inflorescences of Humulus lupulus, also known as hops. This compound is also found in beer and belongs to a class of compounds that contribute to the bitterness and flavor of hops. Xanthohumol is a prenylated chalconoid, biosynthesized by a type III polyketide synthase (PKS) and subsequent modifying enzymes.

<span class="mw-page-title-main">Humulone</span> Chemical compound

Humulone, a vinylogous type of organic acid, is a bitter-tasting chemical compound found in the resin of mature hops. Humulone is a prevalent member of the class of compounds known as alpha acids, which collectively give hopped beer its characteristic bitter flavor.

<span class="mw-page-title-main">Tetrahydrocannabinolic acid synthase</span> Enzyme

Tetrahydrocannabinolic acid (THCA) synthase is an enzyme responsible for catalyzing the formation of THCA from cannabigerolic acid (CBGA). THCA is the direct precursor of tetrahydrocannabinol (THC), the principal psychoactive component of cannabis, which is produced from various strains of Cannabis sativa. Therefore, THCA synthase is considered to be a key enzyme controlling cannabis psychoactivity. Polymorphisms of THCA synthase result in varying levels of THC in Cannabis plants, resulting in "drug-type" and "fiber-type" C. sativa varieties.

Cannabidiolic acid synthase is an enzyme with systematic name cannabigerolate:oxygen oxidoreductase . It is an oxidoreductase found in Cannabis sativa that catalyses the formation of cannabidiolate, a carboxylated precursor of cannabidiol.

<span class="mw-page-title-main">Lupulone</span> Chemical compound

Lupulone is an organic chemical compound with the molecular formula C26H38O4 and an appearance of a yellow powder which was historically used in beer brewing. However, recent studies have revealed numerous antibacterial and anti-cancer abilities of lupulone.

<span class="mw-page-title-main">Beer chemistry</span> Brewery science and beer chemical composition

The chemical compounds in beer give it a distinctive taste, smell and appearance. The majority of compounds in beer come from the metabolic activities of plants and yeast and so are covered by the fields of biochemistry and organic chemistry. The main exception is that beer contains over 90% water and the mineral ions in the water (hardness) can have a significant effect upon the taste.

Research has shown that Humulus lupulus and Cannabis sativa are closely related, and it may be possible to create novel cultivars of hops that express valuable chemicals similar to commercial hemp. Both hops and cannabis contain terpenes and terpenoids; tetrahydrocannabinol (THC) is a terpenoid. Hops lack the enzyme that could convert cannabigerolic acid into THC or CBD, but it could be inserted using genetic engineering as was done in 2019 for yeast.

Chemical defenses in <i>Cannabis</i> Defense of Cannabis plant from pathogens

Cannabis (/ˈkænəbɪs/) is commonly known as marijuana or hemp and has two known strains: Cannabis sativa and Cannabis indica, both of which produce chemicals to deter herbivory. The chemical composition includes specialized terpenes and cannabinoids, mainly tetrahydrocannabinol (THC), and cannabidiol (CBD). These substances play a role in defending the plant from pathogens including insects, fungi, viruses and bacteria. THC and CBD are stored mostly in the trichomes of the plant, and can cause psychological and physical impairment in the user, via the endocannabinoid system and unique receptors. THC increases dopamine levels in the brain, which attributes to the euphoric and relaxed feelings cannabis provides. As THC is a secondary metabolite, it poses no known effects towards plant development, growth, and reproduction. However, some studies show secondary metabolites such as cannabinoids, flavonoids, and terpenes are used as defense mechanisms against biotic and abiotic environmental stressors.

References

  1. ↑ "Humulus lupulus L.". World Checklist of Selected Plant Families . Royal Botanic Gardens, Kew . Retrieved 2 February 2016– via The Plant List. Note that this website has been superseded by World Flora Online
  2. 1 2 3 Sewalish, Andrew. "Habitat & Adaptation". Humulus lupulus profile. Retrieved 2017-04-13.
  3. 1 2 3 4 Conway, Sean; Snyder, Reid (2008). "Humulus lupulus - Hops" (PDF). College Seminar 235 Food for Thought: The Science, Culture, & Politics of Food. Hamilton College. Retrieved July 31, 2008.
  4. 1 2 "Humulus lupulus (common hop, hops)". Go Botany. New England Wildflower Society. Retrieved 2017-04-13.
  5. ↑ "HerbalGram: Hops (Humulus lupulus): A Review of its Historic and Medicinal Uses". cms.herbalgram.org. Retrieved 2017-04-08.
  6. ↑ "Hop, Humulus lupulus - Flowers". NatureGate. Retrieved 2017-04-13.
  7. ↑ "Hops, Humulus lupulus, plant facts". Eden Project. Retrieved 2017-04-12.
  8. ↑ Burnham, Robyn J. (2014). "Vitis riparia". CLIMBERS: Censusing Lianas in Mesic Biomes of Eastern Regions. University of Michigan College of Literature, Sciences and the Arts. Retrieved 2017-04-02.
  9. 1 2 "Humulus lupulus". NewCROP, the New Crop Resource Online Program. Retrieved 2017-04-02.
  10. 1 2 3 Eriksen, Renée L.; Padgitt-Cobb, Lillian K.; Townsend, M. Shaun; Henning, John A. (December 2021). "Gene expression for secondary metabolite biosynthesis in hop (Humulus lupulus L.) leaf lupulin glands exposed to heat and low-water stress". Scientific Reports. 11 (1): 5138. Bibcode:2021NatSR..11.5138E. doi:10.1038/s41598-021-84691-y. ISSN   2045-2322. PMC   7970847 . PMID   33664420.
  11. ↑ Goese, Markus; Kammhuber, Klaus; Bacher, Adelbert; Zenk, Meinhart H.; Eisenreich, Wolfgang (1999-07-15). "Biosynthesis of bitter acids in hops. A 13C-NMR and 2H-NMR study on the building blocks of humulone". European Journal of Biochemistry. 263 (2): 447–454. doi: 10.1046/j.1432-1327.1999.00518.x . ISSN   0014-2956. PMID   10406953.
  12. 1 2 Natsume, S.; Takagi, H.; Shiraishi, A.; Murata, J.; Toyonaga, H.; Patzak, J.; Takagi, M.; Yaegashi, H.; Uemura, A.; Mitsuoka, C.; Yoshida, K. (2014-11-20). "The Draft Genome of Hop (Humulus lupulus), an Essence for Brewing". Plant and Cell Physiology. 56 (3): 428–441. doi:10.1093/pcp/pcu169. ISSN   0032-0781. PMID   25416290.
  13. 1 2 3 Padgitt-Cobb, Lillian K.; Kingan, Sarah B.; Wells, Jackson; Elser, Justin; Kronmiller, Brent; Moore, Daniel; Concepcion, Gregory; Peluso, Paul; Rank, David; Jaiswal, Pankaj; Henning, John; Hendrix, David A. (2021-02-18). "A draft phased assembly of the diploid Cascade hop ( Humulus lupulus ) genome". The Plant Genome. 14 (1): e20072. doi: 10.1002/tpg2.20072 . ISSN   1940-3372. PMID   33605092. S2CID   231962731.
  14. ↑ Milligan SR, Kalita JC, Heyerick A, Rong H, De Cooman L, De Keukeleire D (June 1999). "Identification of a potent phytoestrogen in hops (Humulus lupulus L.) and beer". J Clin Endocrinol Metab. 84 (6): 2249–52. doi: 10.1210/jcem.84.6.5887 . PMID   10372741.
  15. ↑ Benkherouf, Ali Y.; Soini, Sanna L.; Stompor, Monika; Uusi-Oukari, Mikko (February 2019). "Positive allosteric modulation of native and recombinant GABAA receptors by hops prenylflavonoids". European Journal of Pharmacology. 852: 34–41. doi:10.1016/j.ejphar.2019.02.034. ISSN   0014-2999. PMID   30797788. S2CID   73456325.
  16. ↑ "Hops [CO2] Extract". Toms of Maine. Archived from the original on December 24, 2013. Retrieved 2009-06-06.
  17. ↑ Rozalski M, Micota B, Sadowska B, Stochmal A, Jedrejek D, Wieckowska-Szakiel M, Rozalska B (2013). "Antiadherent and Antibiofilm Activity of Humulus lupulus L. Derived Products: New Pharmacological Properties". BioMed Research International. 2013: 1–7. doi: 10.1155/2013/101089 . PMC   3794639 . PMID   24175280.
  18. ↑ Franco, L.; Sánchez, C.; Bravo, R.; Rodriguez, A.; Barriga, C.; Juánez, Javier Cubero (2012-06-01). "The sedative effects of hops (Humulus lupulus), a component of beer, on the activity/rest rhythm". Acta Physiologica Hungarica. 99 (2): 133–139. doi:10.1556/APhysiol.99.2012.2.6. ISSN   0231-424X. PMID   22849837.
  19. 1 2 "Advancing understanding of hop genome to aid brewers, medical researchers". ScienceDaily. Retrieved 2021-04-09.
  20. ↑ Divashuk, Mikhail G.; Alexandrov, Oleg S.; Razumova, Olga V.; Kirov, Ilya V.; Karlov, Gennady I. (2014-01-21). "Molecular Cytogenetic Characterization of the Dioecious Cannabis sativa with an XY Chromosome Sex Determination System". PLOS ONE. 9 (1): e85118. Bibcode:2014PLoSO...985118D. doi: 10.1371/journal.pone.0085118 . ISSN   1932-6203. PMC   3897423 . PMID   24465491.
  21. ↑ Murakami, A; Darby, P; Javornik, B; Pais, M S S; Seigner, E; Lutz, A; Svoboda, P (2006-05-10). "Molecular phylogeny of wild Hops, Humulus lupulus L." Heredity. 97 (1): 66–74. doi: 10.1038/sj.hdy.6800839 . ISSN   0018-067X. PMID   16685279. S2CID   11920277.
  22. ↑ Pisupati, Rahul; Vergara, Daniela; Kane, Nolan C. (2018-02-21). "Diversity and evolution of the repetitive genomic content in Cannabis sativa". BMC Genomics. 19 (1): 156. doi: 10.1186/s12864-018-4494-3 . ISSN   1471-2164. PMC   5822635 . PMID   29466945.
  23. ↑ Laverty, Kaitlin U.; Stout, Jake M.; Sullivan, Mitchell J.; Shah, Hardik; Gill, Navdeep; Holbrook, Larry; Deikus, Gintaras; Sebra, Robert; Hughes, Timothy R.; Page, Jonathan E.; van Bakel, Harm (2018-11-08). "A physical and genetic map of Cannabis sativa identifies extensive rearrangements at the THC/CBD acid synthase loci". Genome Research. 29 (1): 146–156. doi:10.1101/gr.242594.118. ISSN   1088-9051. PMC   6314170 . PMID   30409771.
  24. ↑ Marks, M. David; Tian, Li; Wenger, Jonathan P.; Omburo, Stephanie N.; Soto-Fuentes, Wilfredo; He, Ji; Gang, David R.; Weiblen, George D.; Dixon, Richard A. (2009-07-06). "Identification of candidate genes affecting Δ9-tetrahydrocannabinol biosynthesis in Cannabis sativa". Journal of Experimental Botany. 60 (13): 3715–3726. doi:10.1093/jxb/erp210. ISSN   1460-2431. PMC   2736886 . PMID   19581347.
  25. ↑ USDA, NRCS (n.d.). "Humulus lupulus var. neomexicanus". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved May 5, 2016.
  26. ↑ "Humulus lupulus". Germplasm Resources Information Network . Agricultural Research Service, United States Department of Agriculture . Retrieved 2018-07-31.
  27. ↑ USDA, NRCS (n.d.). "Humulus lupulus var. pubescens". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team.
  28. ↑ "Humulus lupulus 'Aureus' AGM". RHS Plant Selector. Royal Horticultural Society . Retrieved 25 August 2020.
  29. ↑ "AGM Plants - Ornamental" (PDF). Royal Horticultural Society. July 2017. p. 43. Retrieved 3 March 2018.
  30. ↑ Абаев В. И. Историко-этимологический словарь осетинского языка. Т. 4. М.—Л., 1989. С. 261-262.
  31. 1 2 3 4 "Humulus lupulus". Plant Finder. Missouri botanical Garden. Retrieved 2017-04-12.
  32. ↑ Harper, Douglas. "hop". Online Etymology Dictionary .
  33. 1 2 Behre, Karl-Ernst (1999). "The history of beer additives in Europe - a review". Vegetation History and Archaeobotany. 8 (1–2): 35–48. doi:10.1007/BF02042841. S2CID   129429552.
  34. ↑ Langezaal CR, Chandra A, Scheffer JJ (1992). "Antimicrobial screening of essential oils and extracts of some Humulus lupulus L. cultivars". Pharm Weekbl Sci. 14 (6): 353–356. doi:10.1007/bf01970171. PMID   1475174. S2CID   12561634.
  35. ↑ Schönberger, C.; Kostelecky, T. (2011). "125th Anniversary Review: The Role of Hops in Brewing" (PDF). Journal of the Institute of Brewing. 117 (3): 259–267. doi: 10.1002/j.2050-0416.2011.tb00471.x .
  36. ↑ Plantlife website County Flowers page Archived 2015-04-30 at the Wayback Machine

Bibliography

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