Environmental Engineering Reference
In-Depth Information
1 Introduction
Over the last few years, heavy metals had received considerable attention as a con-
sequence of increased environmental pollution from industrial, agricultural, ener-
getic and municipal sources. They function in the soil as a stress factor causing in
plants physiological disorders after having been absorbed by the root system, which
results in decreased vigor of a plant and retardation of its growth. Physiological re-
sponses of plants to a toxic metal treatment are not only growth inhibition, but also
changes in various biochemical and physiological characteristics (Vassilev et al.
1998
). Many metals have the ability to deteriorate genetic information and chromo-
some structure. The results of such genotoxic effects can be lethality, generation of
mutations, chromosomal aberrations and carcinogenesis (Mišík et al.
2006
,
2007
).
Vascular plants have been found to be highly effective for recognizing and predict-
ing metal stress in the environment (growth inhibition, reduction of biomass pro-
duction, changes in water absorption and translocation (Chatterjee and Chatterjee
2000
; Prasad et al.
2001
; Shanker et al.
2005
; Szárazová et al.
2008
). For genotoxic-
ity studies, plants are highly responsible and sensitive. Their beneficial interest is
that seeds and pollen grains can be easily stored and they offer cheap, and relatively
easy and accurate toxicological assessment (Kristen
1997
). By their ability to ac-
cumulate toxic substances, they indicate metal presence in the environment even in
very low concentration (Chandra et al.
2004
).
2
Material and Methods
Mustard (
Sinapis alba
L.) seeds were germinated in Petri dishes (17 cm diameter,
filter paper with plastic net on the bottom). Tested samples were exposed to 10
varying concentrations (Ni(II) from 1 to 50 mg/L, Cr(III) and Cr(VI) from 5 to
225 mg/L) and tap water (80 mg/L Ca, 27 mg/L Mg; pH = 7.3 ± 0.05) was used for
their dilution. In each Petri dish, 50 healthy seeds of similar size were spread on
the filter paper covered with a plastic net, and overflowed with 50 mL of treatment
solutions or normal tap water as control. The covered Petri dishes were placed in
a thermostat (darkness, t = 25
°
C; air humidity 80 %). After 72 h, root and shoot
lengths were measured.
Basically, the same procedure utilized for growth inhibition was used to deter-
mine the dry mass (DM) and water content (WC). After 72 h, Petri dishes with
germinated seeds were transferred from the thermostat into a laboratory box with a
day-light cycle of 16/8 h and a constant temperature of 23 ± 1 °C. The dishes were
shielded from direct sunlight, and cultivation lasted for 7 days. The shoots were not
in direct contact with tested solutions of metals. After 10 days growth (3 + 7), the
plants were divided into roots and shoots, and fresh mass (FM) was immediately
weighed. The plant material was then oven-dried (t = 80 °C) to constant weight. The
