Humulus lupulus, the common hop or hops, is a species of flowering plant in the hemp family, Cannabaceae. 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.
As the female cone-shaped flowers (hops) are used to preserve and flavor beer, the species is widely cultivated for the brewing industry.
Description
Humulus lupulus is a perennial
herbaceous plant up to tall, living up to 20 years.
It has simple
leaves with 3–5 deep lobes that can be opposite or alternate.
The species is triggered by the longer summer days to flower,
usually around July or August in the Northern Hemisphere.
The plant is
dioecious, with male and female flowers on separate plants. The fragrant flowers are
wind-pollinated.
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.
The fruit is an
achene, meaning that it is dry and does not split open at maturity.
The achene is surrounded by tepals and lupulin-secreting glands are concentrated on the fruit.
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.
Chemistry
H. lupulus contains
myrcene,
humulene,
xanthohumol,
myrcenol and
linalool,
as well as less defined
and
resin.
Hops are unique for containing secondary metabolites, , , and that impact the flavor of the products they are common in, such as beer.
Flowering, growth, and stress response
Predicted genes in homologous primary contigs have been identified as accounting for various traits
Gene expression 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.
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 stress and
Biotic stress) 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.
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
produced that do not impact development or reproduction of hops. Environmental stress has also been shown to reduce
Gene 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.
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
-
Humulus lupulus extract is antimicrobial, an activity which has been exploited in the manufacture of natural deodorant.
-
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.
-
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.
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.
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
DNA sequencing, there is room for more advanced understanding of the plant.
Because of the growing concern of
climate change, and the assumption that there will be an increase of
, 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.
Taxonomy
Relation to Cannabis sativa
The hop is within the same family of plants such as
hemp and marijuana, called
Cannabaceae.
The hop plant diverged from
Cannabis sativa over 20 million years ago and has evolved to be three times the physical size.
The hop and
C. sativa are estimated to have approximately a 73% overlap in genomic content.
The overlap between
includes
Polyketide and prenyltransferases.
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.
Varieties
The five varieties of this species (
Humulus lupulus) are:
-
H. l. var. lupulus – Europe, western Asia
-
H. l. var. cordifolius – eastern Asia
-
H. l. var. lupuloides (syn. H. americanus) – eastern North America
-
H. l. var. neomexicanus – western North American.
-
H. l. var. pubescens – midwestern and eastern North America
Many 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).
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 Vasily Abaev this could be a word of Sarmatian origin which is present in the modern Ossetian language () and derives from proto-Iranian hauma-arayka, an Aryans haoma.[Абаев В. И. Историко-этимологический словарь осетинского языка. Т. 4. М.—Л., 1989. С. 261-262.]
From Sarmatian dialects this word spread across Eurasia, thus creating a group of related words in Turkic, Finno-Ugric, Slavic and Germanic languages (see , Chuvash language хăмла, Finnish language humala, Hungarian komló, Mordovian комла, Avar language хомеллег).
The specific epithet lupulus is Latin for "small wolf".
The English word hop is derived from the Middle Dutch word hoppe, also meaning Humulus lupulus.
Distribution and habitat
The plant is
Native species to Europe, western Asia and North America.
It grows best in the latitude range of 38°–51° in full sun with moderate amounts of rainfall.
Ecology
The flowers attract
butterflies,
amongst other insects.
Animal pests
-
Damson hop aphid ( Phorodon humuli)
-
Two spotted spider mite ( Tetranychus urticae)
-
Japanese beetle ( Popillia japonica)
-
Comma butterfly ( Polygonia c-album)
-
Pale tussock moth ( Calliteara pudibunda)
-
Currant pug moth ( Currant pug)
-
Buttoned snout moth ( Hypena rostralis)
-
Buff ermine moth ( Buff ermine)
-
Spotted lanternfly ( Lycorma delicatula)
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.
Uses
In alcohol brewing
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.
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.
Outside alcohol production
Buds or hops of
Humulus lupulus are used in Iranian ethnomedicine as a
sedative.
In culture
H. lupulus was voted the county flower of
Kent in 2002 following a poll by the wild flora conservation charity
Plantlife.
[Plantlife website County Flowers page ]
Bibliography
-
"Czech hop varieties". Žatec: Chmelařský institut, 2012. on-line
-
Barchet, Ron. "German hops in craft brewing". Wolnzach: Hopfen-Rundschau, 2014.
-
Biendl, Martin. "Hops and health". Wolnzach: German Hop Museum, 2013.
-
Hieronymus, Stan. "For the love of hops: The practical guide to aroma, bitterness and the culture of hops". Boulder, CO: Brewers Publications, a division of the Brewers Association, 2012.
-
Kopp, Sylvia. "Barley & hops: The craft beer book". Berlin: Gestalten, 2014.
-
Melnychuk, M. D.; Boyko, A. L.; Hryhoryuk, I. P.; Likhanov, A. F.; Klyuvadenko, A. A.; Martyn, H. H.; Kukovenko, V. I. "Hop ( Humulus lupulus L.): From cell to plant". Kyiv: Printeko, 2013.
-
Nesvadba, Vladimír. "Development and tradition of Czech hop varietes". Žatec: Hop Research Institute, 2013.
-
Neve, Ray A. "Hops". London: Chapman and Hall, 1991.
-
Skomra, Urszula. "Polish hop cultivars". Puławy: Institute of Soil Science and Plant Cultivation, 2010.
External links
