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Sistema de Información Científica
Red de Revistas Científicas de América Latina y el Caribe, España y Portugal
Rev. Int. Contam. Ambie. 30 (3) 297-305, 2014
TRANSLOCATION OF HEAVY METALS IN
Zea mays
L. TREATED WITH WASTEWATER AND
CONSEQUENCES ON MORPHOPHYSIOLOGICAL ASPECTS
Ahmad Najib KOBAISSI
1,2
*, Ali Ahmad KANSO
2
and Hussein Jaafar KANBAR
2
1
Department of Plant Biology and Environment, Research and Analysis Platform for Environmental Sciences,
Lebanese University
2
Doctoral School of Sciences and Technology, Research and Analysis Platform for Environmental Sciences,
Lebanese University
*
Corresponding author; ahkobeissi@ul.edu.lb
(Received June 2013; accepted June 2014)
Key words: leaves, metal, physiology, roots, stem, wastewater, corn
ABSTRACT
Utilization of treated wastewater has become an alternative for crop irrigation due to fresh-
water scarcity. For that reason, a pot experiment was conducted using treated wastewater
from a Lebanese wastewater treatment plant as an irrigation source to study the effect on
the physical and morphophysiological performance of
Zea mays
L. Treatments with 50 %
wastewater showed superior characteristics for some of the plant’s features, such as leaf
area, plant dry mass, nitrate reductase activity and chlorophyll content; while those treated
with 100 % wastewater negatively affected the plant’s growth. Cadmium was the only
metal that was mostly accumulated in the leaf for all treatments, while other metals were
accumulated in the roots (Na and Fe), stem (Zn and K) or in either root or leaf according
to concentration of wastewater. Major elements to the plant, such as sodium and potassium
were highly accumulated in the plants treated with 50 and 100 % wastewater, nevertheless,
metals were also accumulated (order: Fe > Cu > Cd > Zn), but at lower amounts, and only
cadmium content in the plant is considered harmful to feeding livestock, while zinc is
considered potentially harmful. Finally, proper irrigation with wastewater can boost plant’s
growth, and therefore can be used as an alternative of traditional irrigation.
Palabras clave: hojas, metales, fsiología, raíces, tallo, aguas residuales, maíz
RESUMEN
El uso del agua residual tratada para irrigar los cultivos se ha vuelto una alternativa
común debido a la escasez de agua dulce.
Por esa razón, en este trabajo se presentan
los resultados de un experimento en el que se utilizó el agua proveniente de una planta
de tratamiento de agua residual libanesa, como fuente de riego, para estudiar los efectos
en el desempeño Físico y morFofsiológico de
Zea mays
L. Los tratamientos con 50 %
de agua residual mostraron características superiores para algunos rasgos de la planta,
como el área foliar, el peso seco, la actividad de la nitrato reductasa y el contenido
cloroFílico, mientras que aquellas tratadas con el 100 % de agua residual, mostraron
efectos negativos en su crecimiento. El cadmio resultó ser el único metal que fue
almacenado principalmente en la hoja para todos los tratamientos, mientras que otros
A.N. Kobaissi
et al.
298
metales se acumularon en las raíces (Na y Fe), en el tallo (Zn y K) o en la raíz u hoja,
dependiendo de la concentración del agua residual. Los elementos importantes para
las plantas, como el sodio y el potasio se encontraron en grandes concentraciones en
las plantas tratadas con 50 y 100 % de agua residual, sin embargo, algunos metales
también se almacenaron (en el siguiente orden: Fe > Cu > Cd > Zn), pero en cantidades
menores. Únicamente el contenido de cadmio en la planta es considerado dañino si se
consume, mientras que el zinc es potencialmente dañino. Finalmente, una irrigación
apropiada con agua residual puede promover el crecimiento de la planta y, por tanto,
puede ser utilizada como una alternativa al riego tradicional.
INTRODUCTION
The increasing demand for freshwater, especially
in arid and semi-arid regions, has led to the usage of
alternative irrigation sources, for the population is in
constant augmentation. One of those alternatives is
the usage of treated municipal wastewater. Neverthe-
less, irrigation with wastewater should be thoroughly
thought of before taken into action, since wastewater
contains elements that may alter the normal growth
of plants, such as pathogens, heavy metals and other
pollutants (Gupta
et al.
2008, Simmons
et al
. 2010),
those elements are able to alter the biological processes
(Ikehata
et al
. 2009, Palese
et al
. 2009, Weldesilassie
et al
. 2011) and physicochemical characteristics of
the soil (Angin
et al
. 2005, Segal
et al
. 2011, Tripler
et al
. 2011) and cause over-fertilization of crops, and
thus reduce crop resistance (Hamilton
et al
. 2007).
Yet, treatment with wastewater is capable of improv-
ing soil fertility, and as a result boost crop production
(Rusan
et al
. 2007, Pereira
et al
. 2011). For those
reasons, this experiment was conducted to investigate
the extent of heavy metal translocation in
Zea mays
irrigated with treated wastewater; to detect heavy metal
concentrations in both treated wastewater and maize,
and compare them with standard limits; and lastly to
assess the impact of treated wastewater on the physical
and morphophysiological characteristics of
Z. mays
.
MATERIALS AND METHODS
Plant pot system and plant growth
A pot experiment of twelve randomized PVC
columns, three treatments and four replicates, was
conducted in the Plant Biology and Environment
Department of the Lebanese University. Each PVC
column, of 15 cm diameter, was ±lled with a 40 cm
layer of air-dried and 7 mm meshed clay loam soil. A
subsample of the soil was used to determine chemical
and physical properties. Each treatment was irrigated
with 500 mL/week on two steps, the three treatments
consists of three irrigation solutions: T1: 1:0, T2: 1:1
and T3: 0:1 of potable-water:wastewater (v:v). The
wastewater used here was brought from Al-Ghader
station (Lebanon) where only preliminary treatment
had taken place.
In each pot, three pre-germinated seeds were sown
in the soil at a depth of 2 cm. One week after plant-
ing, only the most viable plant was kept in each pot.
During the whole period of the experiment (forty-two
days), environmental conditions were controlled.
A twelve hour photoperiod, 21 ºC temperature and
50-60 % humidity were set. Plants were sacri±ced
42 days after planting. Leaf number and plant height
were recorded, fresh weight of the roots, shoots and
leaves, separately, were taken. In addition, dry weight
(DW) of roots, stems and leaves was determined
after drying at 80 °C in an oven till no more mass
was lost. The plant DW and shoot to root ratio was
calculated. The leaf area was determined by image
analysis software (Image-Pro Plus v4.5; Media Cy-
bernetic, Bethesda, MD, USA). Speci±c leaf area
(SLA in cm
2
/g), leaf mass ratio (LMR), stem mass ratio
(SMR) and root mass ratio (RMR) were calculated ac-
cording to Hunt (1990). The nitrate reductase activity
(NRA) was measured following the method adopted
by Jaworski (1971). Total chlorophyll content of the
leaves was determined via spectrophotometer (thermo
115 spectronic), and calculations were concluded ac-
cording to Arnon (1949).
Metal analysis
The initial soil sample was mixed, dried and
sieved with a 2 mm sieve. It was tested for heavy met-
al content. 0.5 g of each sample were microwave-acid
digested (Speedwave, MWS-2 microwave-system,
BERGHOF) with 1:3 volumes of HNO
3
:HCl (
aqua
regia
). As for the solutions used for irrigation in each
treatment, 2-3 drops of 65 % HNO
3
were added to
each sample prior to metal analysis. Heavy metal
analysis (Cd, Cu, Fe, Pb, Zn) was done by atomic
absorption spectrophotometer (AAS) (RayleiGh-
WFX-210). Cation analysis (Na
+
and K
+
) of the soil
TRANSLOCATION OF HEAVY METALS IN
Zea mays
L.
299
and irrigated solutions was done by fame photometry
(Sherwood - model 420).
As for metal detection in plant parts, 0.5 g of the
dried plant material were microwave-acid digested
with 7 mL of HNO
3
(65 %) and 1 mL of H
2
O
2
(30 %).
The heavy metals in the various parts of the plants
were analyzed using AAS, and sodium and potassium
ions were analyzed by fame photometer.
Statistical analysis
Statistical analyses were performed using SPSS
statistics 17.0. Data were subjected to analysis of
variance (ANOVA) at
P
< 0.05
and
P
< 0.01, Dun-
can’s multiple range test (α = 5 %) and Pearson’s
correlation coeF±cient.
RESULTS
Concentration of heavy metals in the soil and ir-
rigation solutions
The results indicate that all the elements’ concen-
trations in the wastewater are below the maximum
permissible limit (MPL), except for Cd concentration
(
Table I
).
Growth and plant quality
All the corns grew throughout the experiments
regardless of the type of irrigation, however 100 %
wastewater irrigation (T3) reduced plant height (from
127 and 128 cm, in T1 and T2 respectively, to 90 cm),
leaf area and plant dry weight; the last two are sig-
ni±cantly aFFected (
Table II
). As for corn irrigated
with 1:1 tap water:wastewater (T2), some showed
superior characters, though not signi±cant, such as
plant height, leaf area and plant dry weight. Shoot and
root dry weights were signi±cantly diFFerent between
T2 and T3. The greatest variation between all treat-
ments was shown on the shoot/root dry weight ratio
(or total plant dry weight), where the dry weight of
the shoot was lower than that of the root solely in T3.
Fig. 1
shows the variation of the plant part’s
growth with respect to the whole plant. The RMR
showed signi±cant increase when treated with higher
TABLE I.
HEAVY METAL CONTENT FOR TAP WATER, WASTEWATER AND SOIL AND
MAXIMUM PERMISSIBLE LIMITS
Sample
Element
Cd
Cu
Zn
Fe
Pb
Na
+
K
+
Tap water (mg/L)
ND
0.00
0.02
0.02
0.02
0.73
0.06
Wastewater (mg/L)
0.04
0.03
0.32
0.65
0.26
4355
451.25
Initial soil (mg/kg)
0.42
0.87
9.65
282.17
6.1
9.06
0.81
Permissible values for
irrigation water (mg/L)
0.01*
0.2*
2
#
5
#
5*
-
-
MPL soil (mg/kg)
3**
50**
200**
NL**
300**
-
-
MPL: Maximum permissible limit
NL: No limit
ND: Not detected
*: Ayers and Wetcot (1976)
**: USEPA (1997)
#
: from Chiroma
et al
. (2012); WHO (1996)
TABLE II.
VARIATIONS OF PLANT CHARACTERISTICS FOR DIFFERENT TREATMENTS
Treatment
Plant traits
Plant height
(cm)
Leaf
number
Leaf area
(cm
2
)
Shoot dry
weight (g)
Root dry weight
(g)
Plant dry
weight (g)
Shoot/root
ratio
T1
127.67 ± 17.92 a
12.25 ± 1.77 a
988.25 ± 96.52 a 3.72 ± 0.18 a
2.12 ± 0.05 ab
5.84 ± 0.23 a 1.76 ± 0.05 a
T2
128.33 ± 11.78 a
11.75 ± 1.06 a
1177.16 ± 103 a
3.94 ± 0.05 a
2.42 ± 0.08 a
6.36 ± 0.13 a 1.63 ± 0.04 b
T3
90
± 2.83 a
12
± 2.83 a
573.13 ± 75.15 b 1.28 ± 0.22 b
1.68 ± 0.03 b
2.96 ± 0.54 b 0.77 ± 0.01 c
ns
ns
*
**
ns
**
**
Means within columns Followed by the same letter do not diFFer signi±cantly according to Duncan`s multiple range test (α = 0.05).
Signi±cance: **P < 0.01, *P < 0.05, ns: not signi±cant
A.N. Kobaissi
et al.
300
plant, it followed the order of T3 > T2 > T1 (1.016 >
0.932 > 0.862 mg/kg), as did Zn, Na and K (
Table III
).
Copper on the other hand, when treated with 50 or
100 % wastewater showed lower concentrations in
the root when compared to T1 treatments, and pos-
sible complexations of copper had taken place that
made it less likely to be absorbed by the roots. Zinc
and potassium were found in amounts several folds
higher in the stem than in the other two parts. Iron
was greatly absorbed by the root treated with 50 %
wastewater (T1: 57.11 < T2: 103.11 mg/kg), none-
theless it decreased in T3 to 70.64 mg Fe/kg. As for
sodium, it showed highest values in the root in T2 and
T3 treatments. Regarding the three treatments, Zn,
Fe, Na and K followed signi±cantly different behav
-
iors (
Fig. 3
). As for metal concentrations in the whole
plant, cadmium was detected in amounts greater
than permissible limits in all treatments (
Table III
).
T1 and T2 treatments contained zinc a few mg/Kg
below the limit, however T3 was slightly above it.
The mean metal content of each plant was com-
puted per total dry weight (
Fig. 4
). In general, dry
matter produced through T2 and T3 treatments were
concentrations of wastewater (0.36, 0.38 and 0.56 for
T1, T2 and T3 respectively) on one hand, and higher
ratios when compared to leaf and stem mass ratios on
the other, while the other parts, i.e. stem and leaves
showed opposite relation as to the ±rst, with higher
impact on the outcome of the stem growth. As for
the speci±c leaf area, it only showed a signi±cant
increase between T1 and those treated with different
concentrations of wastewater (T2 and T3).
Nitrate reductase activity increased from T1 to T2
to T3, but on a non-signi±cantly basis (120, 126 and
132 ηmol NO
2
/g/h respectively) (
Fig. 2a
). On the other
hand, results show that chlorophyll content increased
signi±cantly (P < 0.05) when treated with 50 or 100 %
wastewater (
Fig. 2b
), and T2 and T3 treatments had
as much as twice total chlorophyll content than T1.
Metal accumulation in corn parts
The mean concentration of cadmium (Cd) was
mostly found to be accumulated in the leaf parts of the
maize, whereas lowest concentrations were found in
the stem for T1 treatment and root for T2 and T3 ones
(
Fig. 3
). Regarding the Cd concentration in the whole
a
100
700
600
500
400
300
200
100
0
T1
a
a
b
T2
T3
80
60
%
SLA (cm
2
/g)
40
T1
0.43
LMR
SMR
RMR
0.20
0.36
0.44
0.17
0.38
0.32
0.10
0.56
T2
T3
20
0
a
a
b
a
a
b
b
c
ab
Fig. 1.
Variation of RMR, LMR, SMR (a) and SLA (b) with different treatments.
Means following the same letter do not differ signi±cantly according to
Duncan’s multiple range test (α = 0.05)
140
T1
T2
T3
a
a
a
a
b
a
b
b
130
120
110
10
0
Chlorophyll (μg/mL)
20
30
40
NRA (ηmol NO
2
/g/h)
100
Fig. 2.
Variation of nitrate reductase activity (a) and chlorophyll content (b) with different
treatments. Means following the same letter do not differ signi±cantly according to
Duncan`s multiple range test (α = 0.05)
TRANSLOCATION OF HEAVY METALS IN
Zea mays
L.
301
found to contain higher metal concentrations than
T1. Sodium and potassium content of T2 and T3
were signifcantly higher (P < 0.05) than T1 (
Fig. 4a
and
b
). While for the rest (Cu, Fe, Cd and Zn), treat-
ments associated with wastewater contained higher
concentrations, though not signifcant (
Fig. 4c-f
).
Therefore, element contents in the plants were the
highest in T3, followed by T2 and lastly T1. Potas-
sium was the highest element to be accumulated from
T1-T2 (548.03 %), while zinc was the lowest (0.53 %)
(
Table IV
). T2-T3 metal accumulation, however,
witnessed sodium as the highest accumulation, while
iron was the lowest. The degree of accumulation in
T1-T2 is: K > Na > Fe > Cu > Cd > Zn, T1-T3 fol-
lows the same order, while T2-T3 showed a different
one (Na > K > Zn > Cu > Cd > Fe).
Pearson’s correlation showed the presence of
certain correlations between different metals on one
hand, and different plant physical features on the
other (
Table V
). Fe and K, Zn and Cu, Cd and Cu
and Cd and Zn proved to be positively correlated at
α = 0.01 (r = 0.919, 0.929, 0.945 and 0.983 respec
-
tively), while sodium and potassium and iron shared
a correlation signifcant at α = 0.05. Nonetheless, all
relations seemed to be positively correlated, opposing
Na content in the plant and S/R ratio (r = –0.850).
As for the physical features, shoot dry weight was
strongly correlated with all other physical features,
indicating its vulnerability to other changes that are
caused by the usage of wastewater as irrigation.
DISCUSSION
The irrigation solutions used in this experiment,
whether pure wastewater, tap water or the 50 % mix,
a
a
aa
a
a
a
a
a
a
a
b
b
a
a
a
100
80
60
%
40
Cd
Cu
T1
0.31
Leaves
Stem
Root
0.25
0.3
6.11
25.2
11.9
944
823
921
449
632
209
10.3
8.91
57.1
1.25
1.03
1.8
Zn
Fe
Na
K
20
0
a
a
a
a
a
a
a
b
c
a
a
b
a
c
b
a
a
a
100
80
60
%
40
Cd
Cu
T2
0.32
Leaves
Stem
Root
0.32
0.29
7.03
26.7
11.8
508
962
4205
4010
6150
796
10.9
6.28
103
1.29
1.8
1.69
Zn
Fe
Na
K
20
0
a
a
a
a
a
a
a
b
c
a
a
b
a
b
b
a
a
a
100
80
60
%
40
Cd
Cu
T3
0.36
Leaves
Stem
Root
0.33
0.33
9.56
29
12.7
540
990
4420
4640
6380
697
14.6
11.8
70.6
1.83
1.3
1.64
Zn
Fe
Na
K
20
0
a
a
Fig. 3.
Metal partitioning (in mg/kg) in the root, stem and leaves in different treatments. Means
Following the same letter do not diFFer signifcantly according to Duncan’s multiple
range test (α = 0.05). ANOVA test proved that Zn, ±e, Na and K are signifcantly
different at P < 0.05 between T1, T2 and T3
TABLE III.
METAL CONTENT AND MAXIMUM PERMIS-
SIBLE CONCENTRATIONS OF METALS IN
PLANT
Metal concentration (mg/kg)
Cd
Cu
Zn
Fe
Total Plant
T1
0.86
4.08
43.21
76.31
T2
0.93
4.78
45.48
120.25
T3
1.01
4.77
51.2
97.01
MPL*
0.5
20
50
1000
MPL: Maximum permissible limit for adult livestock feeding
*: WHO (1996)
A.N. Kobaissi
et al.
302
contain elements below the permissible limit, except
the high Cd content in wastewater (
Table I
). Besides
that, they are generally suitable for irrigation. Ir-
rigation with wastewater reduced plant growth by
reducing plant height, dry weight (root and shoot),
shoot to root ratio and leaf area (
Table II
). Previous
works have also reported the effects of wastewa-
ter irrigation on the growth of several ornamental
shrubs, the response observed was species dependent
(Chaiprapat and Sdoodee 2007, Gori
et al
. 2008).
In our case, decreased plant growth was due to the
high salinity content of the wastewater, sodium being
the major saline ion (
Table I
). Corn shoot growth
was more sensitive to wastewater than root growth
(
Table II
and
Fig. 1
), where shoot dry mass was
found, only in T3 case, to be less than root dry mass.
The same result was observed in
Polygala
shoot
growth (Banón
et al
. 2011). Also, Niu and Rodriguez
(2006) observed a decline in S/R when herbaceous
perennials were irrigated with saline water. When the
wastewater was diluted (i.e. T2), the resulting water
had higher organic matter and nutrient content than
tap water treatments, for this reason, a slight amelio-
ration in plant growth was obtained in T2 treatments
(Chaiprapat and Sdoodee 2007). Regarding the S/R
ratio, mixed water reduced the effect of wastewater
in corn, since irrigation with this water resulted in
a greater leaf area than the other two treatments.
Chaiprapat and Sdoodee (2007) found that Chinese
green mustard plants treated with an efFuent blend
had a higher leaf area than those in the control, which
was associated with both the bene±t of nutrients in
the efFuent and an appropriate dilution. In T2 treat
-
ments, a reduction in salt ions, a changed nutrient
concentration or an altered nutritional equilibrium
could have promoted the plant growth in comparison
to T3 treatments. Similar results were reported by
Day
et al.
(1979) who observed that wheat irrigated
with treated wastewater produced taller plants and
higher grain yields than did wheat grown with pump
water alone. When the mass ratio of the leaves,
stem and root where calculated, they showed that
T1 and T2 treatments were very similar, however
when compared to T3 ones, it was shown that the
root system was the least to be affected, while the
stem was mostly affected. The SLA in T3 showed a
higher area with respect to leaf mass, meaning that
the thickness of the leaves did in fact diminish when
Fig. 4.
Mean proportion of heavy metal concentration per plant dry mass in different treatments. Means within following
the same letter do not differ signi±cantly according to Duncan’s multiple range test (α = 0.05)
Copper (mg/kg)
Sodium (mg/kg)
Iron (mg/kg)
Zinc (mg/kg)
Potassium
(mg/kg)
4000
3000
2000
1000
0
T1
T2
T3
b
a
b
a
4000
3000
2000
1000
0
b
a
b
b
60
40
20
0
a
a
a
c
3
2
1
0
a
a
a
d
20
15
10
5
0
a
a
a
e
0.5
0.3
0.4
0.2
0.1
0
a
a
a
f
Cadmium (mg/kg)
TABLE IV.
PERCENTAGE OF METAL ACCUMULATION
PER DRY PLANT BETWEEN DIFFERENT
TREATMENTS
T1-T2
T2-T3
T1-T3
Na
%
119.14
39.61
205.96
K
548.03
21.79
689.29
Fe
68.34
1.42
70.75
Cu
9.13
8.95
18.91
Zn
0.53
9.34
9.92
Cd
5.39
8.68
14.54
TRANSLOCATION OF HEAVY METALS IN
Zea mays
L.
303
treated with 100 % wastewater. Similarly, Bray and
Reid (2002) pointed out the effect of high salinity on
the growth of
Phaseolus vulgaris
. On another note,
Esmailian
et al.
(2011)
observed an increase in chlo-
rophyll content in corn with wastewater irrigation,
and Bergareche
et al.
(1994) and Umebese
et al.
(2009) observed an increased NRA in plants irrigated
with wastewater that could attribute to the high nitrate
content of the efFuent; this was shown in this experi
-
ment, where an increase in the chlorophyll content
and NRA of plants irrigated with mixed water and
wastewater was observed (
Fig. 2
).
The results in
table III
and
fgure 3
indicate
that the accumulation of heavy metals was more
prominent with increasing the proportions of treated
wastewater (the pattern of accumulation follows
the order of T1< T2 < T3). The concentrations of
Cd, Cu, Zn and Fe in the plant under consideration
varied from 0.862 to 1.016, 4.08 to 4.78, 43.21 to
51.2 and 76.31 to 120.25 mg/kg, respectively at
different irrigation regimes. Cd reached a level
higher that permissible according to WHO, and
Zn in T3 treatment was above MPL, while the rest
were all below the MPL. Heavy metals present in
the efFuents used for irrigation tend to accumulate
in the soils, become bio-available and eventually get
translocated to plants (Toze 2006). Similarly, Shat-
anawi (1994) found that heavy metals increased in
eggplant fruit and leaves when using treated waste-
water irrigation, which con±rms the ±ndings that the
treated wastewater was also a factor in boosting the
heavy metal accumulation in the plant parts (
Fig. 4
),
other researchers also reported an increase in
micronutrients uptake by the plant when irrigated
with sewage water (Brar
et al
. 2002, Mohammad
and Mazahreh 2003).
The heavy metal accumulation and translocation
potential is plant and metal dependent. Moreover,
heavy metals in soils occur in complicated forms be-
cause of their association with organic and colloidal
forms that in turn inFuence their availability (Li
et al.
1995). Some researchers found that the presence of Zn
can inhibit Cd adsorption and thereby cause low Cd
accumulation in plants, especially in the roots (Adri-
ano 1986, Nan
et al
. 2002). The results in
fgures 3
and
4
indicate that corn was able to accumulate a
certain amount of Zn. Sharma
et al.
(2004) also re-
ported that Fe concentration reduced the uptake of
metals, particularly Cd. The high concentration of
Fe accumulated in the roots of corn may be attrib-
uted to the microbial consortium in the roots, which
excrete organic acids that facilitate the absorption
and accumulation of Fe in the roots, as reported by
Crowley
et al.
(1991). In this study, K accumulated
in various parts of the crops. The order of potassium
accumulation is stem > leaf > root, and for sodium
root > stem > leaf in T2 and T3. Disregarding sodium
and potassium accumulation in the plant, Fe and Cu
were the highest to accumulate (
Table IV
), followed
by Cu then Zn, Masona
et al.
(2011) also reported
that Fe was the highest metal to accumulate in the
corn. Berry
et al.
(1980) found that heavy metals
taken up by vegetables grown with wastewater tend to
mostly accumulate in the roots, as is the case of iron,
sodium, and copper (
Fig. 3
), and only a fraction of the
heavy elements absorbed is translocated to the top.
TABLE V.
PEARSON’S CORRELATION COEFFICIENT SHOWING RELATIONSHIP BETWEEN METALS AND PLANT
GROWTH
Correlations
Leaf area
Na
K
Cu
Fe
Zn
Cd
Height
DMs
DMr
DMt
S/R
Na
1
.820
*
.487
.885
*
.405
.437
–.735
–.713
–.335
–.643
–.850
*
–.555
K
1
.385
.919
**
.260
.334
–.304
–.226
.169
–.143
–.432
–.008
Cu
1
.686
.929
**
.945
**
–.398
–.100
.237
–.027
–.219
–.093
Fe
1
.591
.657
–.527
–.340
.083
–.253
–.534
–.144
Zn
1
.983
**
–.525
–.124
.115
–.073
–.209
–.076
Cd
1
–.510
–.108
.152
–.052
–.209
–.029
Height
1
.869
*
.729
.854
*
.879
*
.730
DMs
1
.890
*
.995
**
.975
**
.940
**
DMr
1
.931
**
.774
.860
*
DMt
1
.949
**
.940
**
S/R
1
.878
*
Leaf area
1
*correlation is signi±cant at α = 0.05
**correlation is signi±cant at α = 0.01
A.N. Kobaissi
et al.
304
Fazeli
et al
. (1991) provided evidence that the ac-
cumulation of heavy metals in different parts of the
plant body might be due to the tendency of different
parts of the plant to accumulate certain amounts of
metals, while Ardakani
et al.
(1988) reported that
plant species and plant parts infuence the uptake and
accumulation of heavy metals by plants. In this study,
a strong and positive correlation was found between
cadmium and zinc content in the plant (
Table V
), Og-
bonna and Nwosu (2011) found a same relationship;
however it was between cadmium in the plant and
zinc in the soil. Nevertheless, the presence of a certain
metal in the plant may alter the presence of another.
CONCLUSION
This report clearly shows how maize treated with
wastewater decreased its performance, especially
plants treated with 100 % wastewater (i.e. T3), where
leaF area and total dry weight oF were signi±cantly
reduced, with higher effect on the shoot than root.
Wastewater also boosted the physiological response
of
Z. mays
in terms of leaf area, NRA and total chlo-
rophyll content, the last showed great increase when
as much as 50 % wastewater was added. Cadmium
was the only metal that was found above MPL in the
whole plant in all treatments, and thus can cause a
threat to feeding livestock, while Zn content in T3
plants might possibly pose a threat. Zn was mostly
found in the stem, Fe in the roots, Na in the roots for
plants treated with wastewater and Cd in the leaves
and stem. K and Na accumulated the highest in the
plant followed by Fe, Cu Cd and Zn. In conclusion,
wastewater can be suitable for irrigation if the content
of heavy metals and other contents are limited to non-
destructive infuence, but can cause serious growth
deterioration if containing elemental concentrations
that prove themselves unconstructive to the plant.
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