Bt Research 2012, Vol.3, No.3, 11
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Figure 2 Scanning electronic micrographs showing colonization of
different strains of
B. thuringiensis
in different parts of cabbage
seedlings
Note: A: Cabbage Seedlings of non-infected control leaves by
B.
thuringiensis
;
B: Presence of cracks in roots of cabbage seedlings
with spore and bipyramidal crystals (cb) of strain S1905 of
B.
thuringiensis
;
C: Vegetative cells, spore and spherical crystals of
B.
thuringiensis
strain S1905 aggregated colonizing leaves of cabbage
seedlings; D: Colonization of roots of cabbage seedlings by spores
and bipyramidal crystals (cb) of
B. thuringiensis
kurstaki
HD-1
S1450; Bars:A: 10 µm; B: 5 µm; C: 5 µm; D: 2 µm
Figure 3 Scanning electronic micrographs showing colonization by
B. thuringiensis
strains in different parts of cabbage seedlings
Note: A: The presence of the spore of
B. thuringiensis
S2124 in
stomata of stems of cabbage seedlings; B: The colonization of
vegetative cells (cv), spore (ep) and spherical crystals of
B.
thuringiensis
S1905 in depressions and stomata of leaves of
cabbage seedlings; C: Spherical crystals of B
.
thuringiensis
S2122 in xylem of roots of cabbage seedlings; D: Formation of
fibrils in spores of
B. thuringiensis
strain S2124 colonizing
stems of cabbage seedlings; Bars: A: 5 µm; B: 20 µm; C: 5 µm;
D: 2 µm
Figure 4 Autoradiography of cabbage seedlings after five days exposed to
B. thuringiensis
strains
Note: A: Control; B: S1450; C: S1905; D: 2122; E: S2124-Btk standard; They are showing the colonization of
B. thuringiensis
marked with methionine
35
S in roots, stems and leaves of cabbage seedlings
with
B. subtilis.
However, other studies with
B.
subtilis
indicated an increase in
Eucalyptus
seed
germination (Campello, 1992). This demonstrates that
bacterial strains can have different effects depending
on the plant and the bacterium used; the time the seed
is exposed to treatment may also have an effect, since
mechanisms such as nitrogen fixation, production of
phytohormones, competition, and control of plant
pathogens, among other aspects, may be involved
in the regulatory process of plant growth (Sabino
et al., 2000).
The strains of
B. thuringiensis
studied here did not
promote growth of cabbage seedlings under the tested
conditions and the bacterial strains did not present a
positive effect. Although work carried out with
bacteria applied to seeds, using another bacterium of
the genus
Bacillus
,
B. amyloliquefasciens,
demonstrated
an improvement in the quality of cucumber (
Cucumis
sativus
)
seedlings (Silveira et al., 2004).
