Agriculture Reference
In-Depth Information
Based on the percentage of growth inhibition, the 41 isolates obtained were classified as:
sensitive (growth inhibition - 80-100%), moderately tolerant (growth inhibition - 60-80%)
and tolerant (growth inhibition - <60%).
Pb
3mM
Cd
1mM
As
6mM
7,1%
7,1%
14,3%
42,9%
BC
50,5%
78,6%
100%
12,5%
6,3%
43,8%
BA
56,3%
31,3%
50,0%
100%
18,2%
36,4%
36,4%
BD
63,6%
63,6%
81,8%
Growth Inhibition (%)
< 60
60-80
80-100
Figure 2. Percentage of isolates exhibiting a growth inhibition <60% - tolerant, 60-80% - moderately
tolerant and 80-100% - sensitive in the different locations, for non-essential metals: Pb, Cd and As.
Figure 2 shows the percentage of sensitive, moderately tolerant and tolerant isolates in
each location, for the concentration where all isolates still showed growth, to non-essential
metals (Pb - 3 mM, As - 6 mM and Cd - 1 mM). Generally, isolates showed high sensitivity
to Cd, since growth was severely inhibited at 1 mM for all isolates of BC and BA soils and to
2/3 of BD soil, and moderately tolerance to As, as in the three soils the percentage of
sensitive isolates to 6 mM As was similar (between 36.4% and 43,8%). Pb was the metal
where tolerance differences between soils were more marked. BC isolates showed the highest
tolerance, since only 14.3% of them were sensitive to Pb.
Rhizobium
BD population showed
the lowest tolerance, being more than 80% of the isolates sensitive to 3 mM Pb.
Figure 3 shows the percentage of sensitive, moderately tolerant and tolerant isolates in
each location for the essential metals (Ni - 0.5 mM, Cu - 0.5 mM and Co - 0.5 mM). Once
