Joint International Conference on Long-term Experiments ...

Fig. 1 – Formation of somatic embryos and
embryo clusters on the cotyledonnary explant
Fig. 2 – Stable oak embryogenic
culture
Besides embryogenesis, other reactions of the explants to the culture conditions were
observed: callogenesis, rhyzogenesis and germination.
The viability of explants after two subcultures ranged between 55 to 85% at the young
explants (stage and 2), and 71 to 100% in the case of more developed explants (stages 3
and 4). The differences between species and provenances, concerning the viability were
due mostly to technical reasons (distance to the field, number of days in conservation
before dissection, etc.).
All records concerning the efficiency of somatic embryo induction and the
frequency of other reaction of the explants were reported only to the viable explants.
It was found that the most important factor affecting the somatic embryo induction
efficiency was the developmental stage of the explant. In all oak species, the
embryogenic ability decreased constantly from the youngest to the more advanced
zygotic embryos used as explants (Fig. 3). The same trend was recognised in the case of
the provenances inside the species, regardless the culture medium used for the induction
(Fig. 4 and 5).
% embryogenic induction
50
45
40
35
30
25
20
15
10
5
0
Stage 1 Stage 2 Stage 3 Stage 4
explant type (developmental stage of zygotic embryo)
Q. robur
Q. petraea
Q. frainetto
Fig. 3 - The effect of explant type (developmental stage of zygotic embryo)
upon the embryogenic ability, in three Quercus species
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