Agriculture Reference
In-Depth Information
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Hemp Breeding Department at the
morphological differences and are therefore
described as sexually dimorphic.
An important stage in the development of
hemp was the discovery of monoecious plants.
Monoecious hemp exhibits the same structure
of male and female plants as the dioecious
plant, except that both male and female
flowers are found on the same stem (Fig. 4.4).
Monoecious hemp with male and female flow-
ers on the same plant can occur spontaneously
in dioecious hemp populations/cultivars in a
very low ratio, usually less than 10-20 plants/ha.
According to Hoffmann (1938), this fre-
quency is 0.1%. The phenotype of monoe-
cious hemp plants is very similar to that of
the dioecious female plants. The monoecious
form can be defined as an artificial form of
hemp because, even without human interfer-
ence, it returns progressively to the dioecious
state.
Several transitional stages may also be
observed between these two basic sexual forms
of hemp (dioecious and monoecious).
Dioecious hemp results entirely from
cross-pollination: the seeds produced by female
plants are the result of pollination of the seed
Institute of Bast Crops, Glukhov, Ukraine
Fédération Nationale des Producteurs de
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Chanvre - FNPC, Le Mans, France
Institute of Field and Vegetable Crops,
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Novi Sad, Serbia
Institute of Natural Fibres, Pozna ´, Poland
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4.2.2 The selection of hemp
Reproductive biology of hemp
The selection techniques in use are determined
by the reproductive biology of the hemp plant.
Hemp typically reproduces by sexual reproduc-
tion but, in certain cases, parts of the plant can
be used for asexual reproduction. Hemp is
naturally dioecious. Dioecious hemp presents
as two types of plant, one with female flowers
and the other with male flowers (Fig. 4.3). The
ratio of sexes (the number of male to female
plants) in a dioecious population is close to
1:1. The male and female plants demonstrate
Fig. 4.3.
Sexual dimorphism of dioecious hemp.
Male flowers (top left) and female flowers
(top right). The appearance of the two plants can
be compared side by side (bottom).
Fig. 4.4.
Monoecious hemp showing female
(a) and male (b) flowers on the same stem.
