Agriculture Reference
In-Depth Information
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The first initiative concerned harvesting,
on all the stems and, as has been mentioned
already, the possibility of harvesting a uniform
stand mechanically.
Another consequence of hemp plasticity is
its variable maturation: certain varieties flower
early, whereas others flower much later. This
allows hemp to adapt easily to different latitudes.
Geographically, in France, hemp cultiva-
tion is limited today to a score of departments,
situated principally in the west, centre, south-
west and especially the east (the Aube prima-
rily) of the country.
which evolved from manual methods
towards an entirely mechanized cultiva-
tion, ending with fibre extraction under-
taken in a workshop. This initiative was
only made possible by the concurrent
development of monoecious varieties that
were suited for mechanical harvest.
The second initiative consisted of develop-
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ments in the use of hemp fibres for use in
the manufacture of fine and resistant
paper (speciality papers). Between 1970
and 1994, this industrial sector was the
only one to use hemp, requiring the culti-
vation of only a few thousand hectares
yearly. Since then, the industrial sectors
using fibres have grown and we have wit-
nessed the diversification of possible
opportunities and uses and devised new
openings for hemp fibres and its
by-products.
Hemp currently is employed on an industrial
scale and has represented approximately
10,000 ha/year in France since the start of the
21st century.
19.4 Chemistry
Due to its botanical, chemical and pharmaco-
logical uniqueness, hemp has been and contin-
ues to be the subject of numerous studies.
During the 1970s, the United Nations substan-
tially funded studies on hemp. As a conse-
quence, hemp is today one of the best-known
plants. This fact was demonstrated well in
1980 by the publication of a review article that
provided an inventory of all the constituent
chemicals that had been identified (Turner
et al
., 1980): 421 compounds were identified,
belonging to different phytochemical groups
including nitrogen-containing compounds,
fatty acids, steroids, terpenes (mono-, sesqui-,
di- and triterpenes), flavonoids, vitamins, pig-
ments and of course around 60 cannabinoids,
the specific terpenes of hemp (Turner
et al
.,
1980; Seth and Sinha, 1991). The three most
important are (Fig. 19.1):
delta-9-tetrahydrocannabinol (
19.3 Botany
Hemp (
Cannabis sativa
L., Cannabaceae) is
an annual herbaceous plant with iconic
palmate-lanceolate leaves. The flowering tips
are mixed with foliate bracts. The leaves, and
in particular the bracts, are the only parts of
the plant with secretory hairs, producing a
resin whose chemical composition is complex.
One of the main characteristics of hemp is
its malleability: when grown under favour-
able conditions (soil, water, sunlight), it can
attain a height of 5-6 m and a span of 2-3 m.
Industrially cultivated varieties, however, are
sown densely (50 kg of seed/ha) and their
foliar development is therefore limited.
Consequently, they rarely exceed 2-2.5 m in
height.
Even though hemp is naturally a dioecious
species, contemporary industrial varieties are
almost entirely monoecious (plants have sepa-
rate male and female flowers on each plant).
This presents a number of agronomic advan-
tages; most notably, the production of seeds
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Δ-9-THC),
responsible for the psychoactive proper-
ties of the plant, whose concentration
therefore needs to be known;
cannabidiol (CBD), which is the main can-
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nabinoid in hemp cultivated in France and
has no psychoactive properties;
cannabigerol (CBG), the biogenetic pre-
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cursor of the previous cannabinoids, also
devoid of any psychoactive properties.
It should be noted that it is due to the presence
of the classified substance,
-9-THC, that
hemp is also classified as a narcotic.
Numerous studies have demonstrated
that the relative proportions of the main
Δ
