Agriculture Reference
In-Depth Information
ammonium quaternary
OH
OH
N
+
O
trigonelline
+
choline
N
Spermidines
Amines
H
N
N
hordenine
piperidine
O
H
N
H
N
H
OH
N
HO
H
OH
cannabisativine
Fig. 3.15.
Principal alkaloids derived from Cannabis leaves (from Turner, 1980).
phytochemistry is equally rich, yielding second-
ary metabolites with uses in both pharmacol-
ogy and chemistry. With the current focus on
the preservation of biodiversity, the opportuni-
ties for the controlled and reasoned exploita-
tion of hemp's fibre and molecular potential
are clear for all to see.
and flowering. These were thought to be
influenced by changes in day length.
Starting in 1910, the Frenchman, Julien
Tournois, undertook a series of experiments
that changed the focus of research in this field.
Working initially on the hop (
Humulus
) plant,
he discovered that when this plant was grown in
the winter, protected by a cold frame, the differ-
ent developmental phases were shortened and
the final flowering phase occurred more rapidly.
Extending his study to the hemp (
Cannabis
)
plant, he again observed a significant reduction
in the length of these developmental phases.
After undertaking various checks, and
taking care to compare the cultivars in winter
and in summer, with the latter being deprived
only of light, Tournois was able to conclude
that day length was the only environmental
factor responsible for the observed phenom-
ena (Tournois, 1912). He is therefore credited
with the discovery of photoperiodism, which is
later explained by Garner and Allard (1920),
following their work on soybean and tobacco.
Further experimental work by Garner and
Allard allowed them to propose a classification
system of plants according to their response to
day length:
Long-day plants (hemeroperiodic) - long
3.5
Part III: The Vegetative Cycle
3.5.1
Hemp and photoperiodism
Discovery of the phenomenon
As early as the end of the 19th century, a
number of authors remarked on the anoma-
lous sex ratio of hemp plants or on the anom-
alies identified in the organogenesis of hemp
plants when vegetating under environmental
conditions that differed from those of normal
cultivation. The tendency of most authors
was to seek the explanation in the ground
and in differences in the composition and
nutritional properties of the soil. Generally
speaking, observations made on a number of
species suggested that a 'substance' might be
acting to control a number of key vegetative
phenomena: including germination, growth
•
day, short night produces flowering.
