Environmental Engineering Reference
In-Depth Information
Fig. 4.3
Water content (g/g DM) in roots and shoots of
S. alba
L. seedlings after 10 days growth
in the presence of tested metals; mean of three determinations, standard deviation 6 % or less (
R
—
root;
S
—shoot;
Con.
—control)
of shoots. This indicates a reduction in water uptake (Fig.
4.3
). Water content in
both plant parts was reduced very rapidly in comparison to that in control seedlings,
and varied significantly with the tested concentrations. Because the water content
in the shoots was significantly reduced in the presence of tested metals, it can be
concluded that Cr and Ni inhibited not only water absorption by the roots, but also
water tranport into the upper seedling parts. These results disagree with Chatterjee
and Chatterjee (
2000
) conclusion, that excess Cr decreases the water potential and
transpiration rates and increases diffusive resistance and relative water content in
the leaves of cauliflower. However, Barcelo et al. (
1986
) observed a decrease in leaf
water potential in a Cr-treated bean plant. Decreased turgor and plasmolysis was
also observed in the epidermal and cortical cells of bush bean plants exposed to Cr,
because toxic levels of Cr decreased tracheary diameter in vessel-bearing plants,
thereby reducing longitudinal water movement (Vazquez et al.
1987
).
3.2
Genotoxicity Study
Toxic effects of heavy metals, mainly during chronic exposure, are not visible im-
mediately. Hence, eco-toxicological studies suggest the assessment of genotoxicity.
Genotoxicity effect is developed as early as the concentration is lower than that for
phytotoxicity effect (Mičieta and Murín
1998
). For phytotoxicity and clastogenicity
study,
V. sativa
seedlings were used. Phytotoxicity was determined through IC
25
,
IC
50
and IC
75
values and for roots and shoots the strongest inhibitory effect, pursuant
to
S. alba
, had Ni(II) (Fig.
4.4
). However, Cr(VI) inhibited
V. sativa
root growth less
