This research was carried out to investigate effect of ethylenediaminetetraacetic
acid and ammonium oxalate on the prevalence of microorganisms and removal of aluminum in
soil by bitter leaf plant (
Vernonia amygdalina). The test plant was sown in aluminium-polluted
soil (conc. = 150mg Al kg
-1 soil). One gram of each chelating agent was dissolved in 1.5 litres
of water and applied at different time intervals; application on a day prior to sowing of test plant
in metal-polluted soil, application on the day of planting, application at one week after planting;
at one month after planting. For the control soils, chelating agent were not added, although
aluminium-contaminated. In the control, aluminium concentrations in leaf tissues were
16.20mg/kg compared to a staggering 9.20mg/kg in EW1 and 5.24mg/kg in OD1. However,
heavy metal concentration of the leaves of
Vernonia amygdalina in the control, EW1, EM1,
OD-1 and OW1 were significantly similar (P>0.05). Concentration of aluminium in the stem
tissues were also similar in ED1, EM1, OD-1, OD1 and OW1 (P>0.05) were concentration
ranged from 5.42mg/kg to 7.98mg/kg. Compared to the control, aluminium concentration in
stem tissues was 4.95mg/kg comparable with 3.42mg/kg in OM1. In the plant root, OD1 had the
highest accumulation of aluminium in the root (16.92mg/kg); however concentrations of
aluminium in the roots were also statically similar in OW1 (15.08mg/kg), OM1 (13.84mg/kg),
OD-1 (14.72mg/kg), EM1 (15.12mg/kg) and in the control (13.52mg/kg). Results of the
following also showed concentrations of residual aluminium in the soil ranging from
68.25mg/kg in the control to 109.85mg/kg in ED1 soil. After three months of planting, results
show that the total bacteria count for ED1 (5.3 × 10
4 cfu/g) had the highest while OM1 (3.9 ×
10
3 cfu/g) had the lowest. For fungi isolates, the highest was control (8.2 × 10
3 cfu/g) whereas
the lowest were OD–1 (6.8 × 10
2 cfu/g). The most prevalent microorganisms in the spiked soil
with heavy metal are
Bacillus subtilis
represented in all the samples for bacteria while
Aspergillus niger
representing fungi. The perseverance of the test plant in the aluminium spiked
soil is an indication of adaptation to the stress imposed by the concentration of aluminium in
soil. In spite of the metal composition within the soil, it was observed that a number of
microorganisms existed. This may therefore suggest a favourable environment for the
microorganisms within the soil rhizospheric region of
Vernonia amygdalina.
