American Journal of Plant Sciences, 2013, 4, 1799-1810
http://dx.doi.org/10.4236/ajps.2013.49221 Published Online September 2013 (http://www.scirp.org/journal/ajps)
Growth of Four Varieties of Barley (Hordeum vulgare L.)
in Soils Contaminated with Heavy Metals and Their
Effects on Some Physiological Traits
Águeda González*, M. Carmen Lobo
Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentación, Madrid, Spain.
Received April 16th, 2013; revised May 17th, 2013; accepted June 19th, 2013
Copyright © 2013 Águeda González, M. Carmen Lobo. This is an open access article distributed under the Creative Commons At-
tribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is prop-
erly cited.
ABSTRACT
To evaluate the effect of zinc (Zn), cadmium (Cd), and chromium (Cr) on growth and selected physiological traits in
barley, a greenhouse trial was performed using four barley varieties that were exposed to different concentration of
these metals. The parameters quantified were growth, chlorophyll content, and chlorophyll fluorescence during three
phenological stages: flag leaf, anthesis, and grain filling. The metal concentrations in both the plant and soil were also
quantified. We determined that the varieties studied were more tolerant to Zn and Cd than to Cr. Treatment with Zn did
not negatively affect growth, and only high concentrations of Cd decreased growth by approximately 4% to 8%. Plants
treated with the highest Cr concentration stopped growing at the flag leaf stage. The amount of metal that accumulated
in the plant increased with increasing metal concentration, and the highest amount of accumulated metal was recorded
in the root and shoot. Both the plant height and dry weight were higher in the CB502 variety plants, followed by the
Reinette, Pedrezuela, and Plaisant varieties. The same trend was observed for the chlorophyll content and fluorescence,
with a significant correlation between the growth parameters and chlorophyll content (p < 0.001). Thus, we determined
that barley has variability in the studied traits.
Keywords: Growth; Heavy Metal; Barley; Chlorophyll Content
1. Introduction
Environmental quality is increasingly affected by heavy
metals present in the atmosphere, water, and soil. For this
reason, the interest in understanding the toxic effects of
heavy metals on crop growth and physiology has in-
creased in the past few years.
All plants absorb heavy metals from the substrate in
which they grow to different degrees. The metal concen-
trations in different parts of the plant depend on intrinsic
(genetic) and extrinsic (environmental) factors and vary
widely between the species and types of metal. Plants
can tolerate large amounts of metal in their environment
using two strategies: 1) Exclusion: The metal transport is
restricted and minimal, and the metal concentration in the
shoot remains relatively constant even within a wide
range of metal concentrations in the soil. This is the most
common strategy in species that are tolerant to metals; 2)
Accumulation: Metals accumulate in a non-toxic form in
the upper parts of terrestrial plants for both high and low
concentrations present in the soil [1-3]. The ability of ter-
restrial plants to absorb contaminants from the rhizo-
sphere and move them to the shoot has resulted in an
increase in the number of studies on plants that can im-
prove soils contaminated by heavy metals [4-7].
The use of crops for phytoremediation has the advan-
tages of producing large amounts of biomass and a great
adaptability to different environmental conditions. How-
ever, to be effective, the plants must be tolerant to con-
taminants and must also be capable of accumulating
large amounts of toxic elements in their tissues [8]. If the
concentration of contaminants in the crop biomass is
below the critical level for cattle consumption, these
crops can add important economic value to the extraction
process. The phytoextraction of metals is a promising
method that is applicable to soils that are mildly or mod-
erately contaminated, and this is an alternative to ex-situ
*Corresponding author.

Growth of Four Varieties of Barley (Hordeum vulgare L.) in Soils Contaminated with
Heavy Metals and Their Effects on Some Physiological Traits
1800
decontamination methods, which are both expensive and
environmentally damaging [2,3,9].
For phytoextraction, two groups of plants were con-
sidered: hyper-accumulating species that are capable of
accumulating and tolerating high levels of metals, and
species that produce large amounts of biomass, which
compensates for their lower metal accumulation in tis-
sues. In the latter group, cereal crops are increasingly of
interest for phytoextraction processing of heavy metals
[10-13]. Advances in plant improvement through genetic
engineering, which can modify traits including absorp-
tion, transport, accumulation, and tolerance of metals,
have opened new possibilities for phytoremediation [7,14,
15].
Hyper-accumulating plants are, by definition, hyper-
tolerant to metals that accumulate in the shoot; however,
some genetic studies suggest that accumulation and tol-
erance are independent traits [16]. In reality, accumulat-
ing plants must have both traits to potentially accumulate
large amounts of metal [17]. A plant that is only capable
of accumulating is unlikely to survive in environments
with high levels of available metals.
Hyper-accumulating plants are much more efficient at
translocating metals from the roots to the shoot than
plants that are not hyper-accumulating. This can be ex-
plained by the lower sequestration of metals into root
vacuoles, which is typical of non-accumulating plants, or
by more efficient transport through the xylem [2].
Plant capacity for accumulating Cd, Cr, and Zn differs
between genotypes [12,18-20]. The existence of variabil-
ity, together with evidence that phytoextraction is a pro-
mising technique applicable to moderately contaminated
soils and is an alternative to ex-situ decontamination,
suggests that phytoremediation can offer a viable solu-
tion to metal-contaminated soils.
The goals of this study were as follows: 1) Evaluate
the effect of different concentrations of Zn, Cd and Cr on
growth in four varieties of barley; 2) Study the relation-
ship between growth and several physiological parame-
ters; 3) Analyze the differences between the barley varie-
ties studied.
2. Materials and Methods
2.1. Plant Materials and Metal Treatments
Four varieties of barley were used. These were two two-
row varieties (Pedrezuela and Reinette) and two six-row
varieties (CB502 and Plaisant). In November 2010, 156
pots of 4 L were planted in the greenhouse with two
seeds per pot. The substrate used contained soil and sand
in a 2:1 ratio. The pots were watered with tap water until
the plants reached stage 20 using Zadoks’ scale [21]. The
pots were then divided into three groups of 34 pots each.
Each group was watered with solutions containing dif-
ferent concentrations of Zn, Cd, or Cr (VI). Four treat-
ments were applied per group (T0, T1, T2, T3) with four
pots per treatment. Control pots (T0) were watered with
400 ml of tap water. The metal treated pots (T1 - T3)
were watered up to the final crop cycle using 300 ml of
tap water + 100 ml of the corresponding metal solution
prepared using ZnSO4·7H2O, CdCl2·2,5H 2O, or K2Cr 2O7
for the Zn, Cd, and Cr treatments, respectively (Table 1).
2.2. Plant Height and Dry Weight
Plant height was measured at the beginning of the treat-
ment (S0), which included the flag leaf stage (i.e., the S1
sampling stage (41 Zadoks)); at anthesis (i.e., S2 sam-
pling stage (65 Zadoks)); and during grain filling (i.e., S3
stage (80 Zadoks)).
At the end of the crop cycle, spikes from each plant
were removed and weighed. Next, the plants were cut at
the soil level to collect the total biomass of the aerial part.
The spikes were threshed in a spike thresher (Precision
Machine Co. Inc.), and the grain obtained was ground
using an IKA A10 grinder for metal analysis. Once
washed, the roots from each plant were dried in a stove at
80˚C for 48 hours to obtain the dry weight.
2.3. Metal Analysis
The metals in the stem and root were extracted after acid
digestion of ashes. The soil metals were extracted in an
acid medium using a microwave extraction system (Mul-
tiwave 3000, Anton Paar GmbH, Graz, Austria). The
analysis of Cd, Zn, and Cr in the corresponding extracts
was performed using Atomic Absorption Spectroscopy
(Varian AA 240 FS, Varian, Palo Alto, CA).
2.4. Chlorophyll Content
The evaluation of the chlorophyll content was performed
in intact leaves using a portable device (SPAD-502). The
samplings were performed at the flag leaf (S1), anthesis
(S2), and grain filling (S3) stages based on the flag leaf
of the main stem from each plant. Four measurements
were extracted per plant, and the mean value was deter-
Table 1. Metal concentration applied by treatment.
Concentration (mM)
Treatment Zn Cd Cr (VI)
T0 0 0 0
T1 50 10 1
T2 150 20 2
T3 250 40 3

Growth of Four Varieties of Barley (Hordeum vulgare L.) in Soils Contaminated with
Heavy Metals and Their Effects on Some Physiological Traits 1801
mined for each leaf.
2.5. Chlorophyll Fluorescence Measurements
Chlorophyll fluorescence was measured at the flag leaf
(S1), anthesis (S2), and grain filling (S3) stages using an
F MS2 fluorometer (Hansatech Instruments Ltd., Eng-
land). Fluorescence parameters were measured in the
central part of the flag leaf of the main stem from each
plant after adaptation to the dark for 30 minutes.
2.6. Statistical Analysis
The data were analyzed using SAS for analysis of vari-
ance. The means between treatments were compared us-
ing a Duncan test or with LSD values.
3. Results
3.1. Effects of Zn, Cd, and Cr on Growth
3.1.1. Pl ant Height
At the beginning of each treatment, the plant heights
were similar between each genotype, with a mean of 42,
33, 32, and 28 cm for the CB502, Pedrezuela, Reinette,
and Plaisant varieties, respectively (Figure 1).
Plants treated with solutions containing a variety of Zn
and Cd concentrations continued to grow until the end of
the grain filling period, with a significantly greater mean
plant height during this period than plant height at the
beginning of the treatments or at the flag leaf stage. The
differences observed in plant height between the anthesis
and grain filling stages were very small and were not
significant in the four genotypes studied. The growth of
the treated plants compared to the growth of the control
plants demonstrated the greatest difference in plants
treated with the highest metal concentrations, which cor-
responded to treatment T3. In CB502 and Pedrezuela
barley, the growth of the control plants was 45% and
50% respectively, similar to that of the plants treated
with the highest Zn concentration. However, in plants
treated with the highest Cd concentration, the growth was
41% for CB502 and 45% for Pedrezuela relative to the
control plants. For the Reinette and Plaisant varieties, the
mean growth of the control plants was 62%. In plants
treated with the highest concentration of Zn, the growth
was 58% for the two varieties. When the highest Cd con-
centration was used, the growth was 54% for Reinette
and 56% for Plaisant.
Treatment with Cr affected plant growth more drasti-
cally in all genotypes studied. The mean height of the
four barley varieties treated with Cr was significantly
lower than the height of plants treated with different con-
centrations of Zn or Cd. As observed in Figure 1, only
plants treated with the lowest concentrations of Cr con-
tinued to grow until the end of the cycle. The growth of
plants treated with the lowest Cr concentration was 27%
for CB502, Pedrezuela, and Reinette, and 32% for Plai-
sant. For the four varieties, the growth was lower than
during treatments with the highest concentrations of Zn
and Cd. The growth of plants treated with the intermedi-
ate Cr concentration was 17% for Reinette and Pedre-
zuela and 7% for Plaisant and CB502. The growth was
0% for plants treated with the highest Cr concentration
for all four of the varieties studied.
3.1.2. Dry Weight
The mean dry weight for the aerial plant parts was great-
est for CB502, followed by Reinette, Plaisant, and Pe-
drezuela. The differences between all four genotypes were
statistically significant (Figure 2A). The dry weights of
plants treated with Zn or Cd were similar and signifi-
cantly higher than the weights of plants treated with Cr.
In plants treated with different concentrations of Zn and
Cd, the dry weight of control plants were very similar or
even lower than the weights of the plants treated with the
highest metal concentrations. Indeed, for Plaisant, the
weights of the plants treated with the highest concentra-
tion of Zn and Cd were 86 g and 109 g, respectively, and
the weight of the control plants was 65 g.
These results are expected because plants treated with
Zn and Cd did not show toxicity symptoms such as leaf
chlorosis until the end of the crop cycle. The leaves on
plants treated with the highest concentrations of Cd dried
earlier relative to the control; however, plants treated
with Cr displayed the toxic effects produced by the metal
across all treatments. Plants that demonstrated the most
severe effect on growth were those treated with the high-
est concentration of Cr. Indeed, these plants dried before
completing the crop cycle. For all varieties studied, the
dry weight of the plants treated with the highest Cr con-
centration was lower than the weight of the controls. The
percent decrease with respect to the control plants was
88%, 87%, 86%, and 79% for CB502, Pedrezuela, Rei-
nette, and Plaisant, respectively.
The dry weights of the roots were higher in plants
treated with Zn and Cd. The dry weight varied between
12% in Reinette treated with Zn and 53% in Plaisant
treated with the highest concentration of Cd (Figure 2B).
The opposite occurred in plants treated with Cr. The re-
duction in root dry weight was recorded in all cases and
was 61%, 77%, 36%, and 40% for CB502, Pedrezuela,
Reinette, and Plaisant, respectively.
The correlation of the dry weight of the aerial parts
and roots was highly significant (r = 0.68; p < 0.001).
The correlations were also significant between the height
and dry weight of the aerial parts (r = 0.85; p < 0.001)
and between the height and weight of the roots (r = dry

Growth of Four Varieties of Barley (Hordeum vulgare L.) in Soils Contaminated with
Heavy Metals and Their Effects on Some Physiological Traits
1802
CB502
T0 T1 T2T3T1T2T3T1T3 T2
Zn Cd Cr
Treatments
S0 S1S2S3
10
30
50
70
90
Height (cm)
Pedrezuela
T0 T1 T2T3T1T2T3T1T3 T2
Zn Cd Cr
Treatments
S0 S1S2 S3
10
30
50
70
90
Height (cm)
Reinette
T0 T1 T2T3T1T2T3T1T3 T2
Zn CdCr
Treatments
S0 S1S2 S3
10
30
50
70
90
Height (cm)
Plaisant
T0 T1 T2T3T1T2 T3T1T3 T2
Zn Cd Cr
Treatments
S0 S1S2 S3
10
30
50
70
90
Height (cm)
Figure 1. Heiht of the plants of four barley varieties at the beginning of treatment (S0) with different concentrations of Zn,
Cd and Cr and sampling in flag leaf (S1), anthesis (S2) and grain-filling period (S3). Vertical bar represents the LSD value at
p < 0.5 for metalxtreatment interaction.

Growth of Four Varieties of Barley (Hordeum vulgare L.) in Soils Contaminated with
Heavy Metals and Their Effects on Some Physiological Traits 1803
T0T1 T2 T3T1T2T3T1T3 T2
Zn Cd Cr
Treatments
CB502
0
Shoot DW (g)
A
T0T0
Pednezuela Reinette Plaisant
10
20
30
40
50
60
70
80
90
100
11 0
120
T0T1 T2 T3T1T2T3T1T3 T2
Zn CdCr
Treatments
CB502
0
Root DW (g)
B
T0T0
Pednezuela ReinettePlaisant
5
10
15
20
25
30
Figure 2. Effect of different treatments of Zn, Cd and Cr on dry weigts of shoot and roots of four barley varieties. Vertical
bar represents the LSD value at p < 0.5 for metalxtreatment interaction.
0.43; p < 0.01).
3.2. Metal Content in Plants
For the Zn (Table 2) and Cd (Table 3) treatments, in all
genotypes studied, the amount of metal accumulated in
the plant increased with increasing metal concentration
applied to the soil. In the Cr treatment (Table 4), signifi-
cant differences exist only between the control and treat-
ments. The correlation obtained between the metal ac-
cumulated in the plants and the concentration of metal
applied to the soil was significant for both Zn and Cr (p <
0.05) and Cd (p = 0.01).
In some genotypes, such as CB502 and Pedrezuela, the
amount of accumulated Cr in the plants treated with the
highest metal concentration was lower than that in the
plants treated with lowest concentrations. This might be
because the precocity of these two genotypes, as plants
treated with higher concentrations dried earlier and there-
fore, stopped accumulating metal.
Significant differences in Zn and Cd accumulation in
different plant parts existed, with higher amounts of
metal accumulated in the root, followed by the shoot and
then the grain, which contained a much lower concentra-
tion of accumulated metal in all genotypes studied (Ta-
bles 2 and 3). There were also differences in the amount
of metal accumulated in the different genotypes studied.
Based on the mean values, the Zn-treated Plaisant plants
accumulated the highest concentration of metal (2698
μg/g), followed by Reinette (1852 μg/g) and CB502 (1464
μg/g). Pedrezuela variety plants accumulated the lowest
amount of Zn (254 μg/g). In the Cd treatments, Reinette
accumulated the greatest amount of metal (958 μg/g),
followed by Plaisant (832 μg/g) and CB502 (707 μg/g).
The Pedrezuela variety plants accumulated the lowest
amount of Cd (405 μg/g).
In the Cr treatment, the metal content in the grains was
not analyzed because, due to Cr’s high toxicity in plants,
the higher concentration treatments dried out before grain
filling.
In Pedrezuela, there were no significant differences
between the amount of metal accumulated in the shoot
and the roots (Table 4). In CB502, Reinette, and Plaisant,
the amount of metal accumuated in the roots was sig- l

Growth of Four Varieties of Barley (Hordeum vulgare L.) in Soils Contaminated with
Heavy Metals and Their Effects on Some Physiological Traits
1804
Table 2. Concentration of Zn in grain, shoots, roots and soil of four barley varieties treated with different concentrations of
this metal.
mM mg/Kg DW
Variety Treatment Grain Stems Root Soil Mean*
CB502 0 30.60 21.37 36.94 386 118.72 d
50 62.10 655.68 1053.38 2437 1052.04 c
150 86.57 1766.06 4586.00 6233 3167.90 b
250 93.99 3666.52 5514.90 8314 4397.35 a
Mean** 68.31 d 1527.40 c 2797.80 b 4342.5 a
Pedrezuela 0 27.64 179.4 56.23 110.2 93.36 b
50 91.46 196.2 330 485.8 275.86 ab
150 94.06 156.5 681 896 456.89 a
250 94.63 282.25 863 1758 749.47 a
Mean** 76.94 a 203.58 a 482.55 a 812.5 a
Reinette 0 25.6 17 39 11.84 23.36 c
50 36.4 931 3165 519.7 1163.025 b
150 27.25 153 8222 1016 2354.56 a
250 21.75 175 9898 1896 2997.68 a
Mean** 27.75 d 319 c 5331 a 860.885 b
Plaisant 0 31.50 32.08 250.73 41 88.82 c
50 79.45 1561.47 4438.68 1550 1907.40 b
150 92.10 5275.24 9219.09 5732 5079.60 a
250 90.34 5352.70 5951.72 9087 5120.43 a
Mean** 73.34 b 3055.37 a 4965.05 a 4102.5 a
*Treatments followed by the same letter do not differ significantly (p < 0.5) Duncan test; **Parts folloved by the same letter do not differ significantly (p < 0.5)
Duncan test.
Table 3. Concentration of Cd in grain, shoots, roots and soil of four barley varieties treated with different concentrations of
this metal.
mM mg/Kg DW
Variety Treatment Grain Stems Root Soil Mean*
CB502 0 0.02 2.51 35.50 0.1 9.53 c
10 5.17 616.12 1951.64 679 812.98 b
20 9.30 1181.51 411.24 1368 742.51 b
40 17.73 1820.63 2429.48 2700 1741.96 a
Mean** 8.05 b 905.19 a 1206.96 a 1186.77 a
Pedrezuela 0 0.60 1.4 16.90 8 6.72 c
10 2.65 300 935 2596 958.41 b
20 3.05 435 856 2580 968.51 b
40 10.3 950 1349 5128 1859.32 a
Mean** 4.15 c 421.6 b 789.22 b 2578 a
Reinette 0 0.02 1 2 5.6 2.15 d
10 0.056 78 1623 1500 800.26 c
20 0.078 85 2287 2844 1304.02 b
40 0.279 165 7251 5244 3165.07 a
Mean** 0.11 b 82.25 b 2790.75 a 2398.4 a
Plaisant 0 1.04 6.13 6.41 0.1 3.41 c
10 5.25 327.93 986.23 732 512.85 b
20 9.86 757.20 1058.24 627 613.07 b
40 33.15 2008.19 4794.90 1455 2072.81 a
Mean** 12.32 c 774.86 b 1711.44 a 703.525 b
*Treatments followed by the same letter do not differ significantly (p < 0.5) Duncan test; **Parts followed by the same letter do not differ significantly (p < 0.5)
Duncan test.

Growth of Four Varieties of Barley (Hordeum vulgare L.) in Soils Contaminated with
Heavy Metals and Their Effects on Some Physiological Traits 1805
Table 4. Concentration of Cr in shoots, roots and soil of four barley varieties treated with different concentrations of this
metal.
mM mg/Kg DW
Variety Treatment Stems Root Soil Mean*
CB502 0 18.02 71.41 1.1 30.18 b
1 684.01 3998.23 72 1584.74 a
2 1373.73 4670.80 57 2033.84 a
3 2244.95 3499.70 52 1932.22 a
Mean** 1080.17 b 3060.03 a 45.52 c
Pedrezuela 0 4.70 10.00 49.2 21.3 a
1 96 110 79.2 95.07 a
2 47.5 255 121.6 141.37 a
3 57.5 40 108.8 68.77 a
Mean** 51.42 a 103.75 a 89.7 a
Reinette 0 6 42.1 58.4 35.5 c
1 320 3098 76.8 1164.93 b
2 362 3837 39.6 1412.87 b
3 364 5310 125.6 1933.2 a
Mean** 263 b 3071.77 a 75.1 b
Plaisant 0 8.84 34.48 0.8 14.71 c
1 516.44 3388.00 93 1332.48 b
2 1132.20 3653.15 106 1630.45 ab
3 1415.45 4692.69 37 2048.38 a
Mean** 768.23 b 2942.08 a 59.2 c
*Treatments followed by the same letter do not differ significantly (p < 0.5) Duncan test; **Parts followed by the same letter do not differ significantly (p < 0.5)
Duncan test.
nificantly higher than that accumulated in the aerial parts
of the plant.
CB502 accumulated the greatest amount of Cr (2070
μg/g) based on the mean values per genotype, followed
by Plaisant and Reinette (1855 and 1667 μg/g, respec-
tively). Pedrezuela accumulated the lowest amount of Cr
(78 μg/g).
The amount of metal that remained in the soil was
greatest for the higher concentration Zn and Cd treat-
ments. The amounts measured in the soil were similar to
those accumulated by the plants in the roots or in the
shoot. However, in the Cr-treated plants, less metal re-
mained in the soil; this result was different for the dif-
ferent treatments and genotypes, an effect likely due to
the higher toxicity of Cr in plants.
3.3. Chlorophyll Content
The chlorophyll content in plants treated with different
Zn concentrations was higher during the flag leaf and
anthesis stages compared to the last sampling period,
which was performed at the end of the grain filling pe-
riod (Table 5). In the latter sampling period, the meas-
urements were significantly lower in the four varieties
studied. The differences between the control and the
higher concentration treatments were small, with the
highest measurements being those obtained in plants
treated with the highest metal concentration, except for
the Reinette variety, where the measurements did not dif-
fer from the control measurements.
Based on the mean values, the varieties can be sepa-
rated into two groups. CB502 and Reinette had similar
mean chlorophyll contents (45.89 and 45.35, respec-
tively), which were significantly higher than the values
obtained for Plaisant and Pedrezuela (41.99 and 35.40,
respectively).
In the Cd treatments (Table 6), we observed the same
trend found in the Zn treatments. The chlorophyll content
measured in the last sampling period (S3) was signifi-
cantly lower than those measured for the previous sam-
pling periods (S1 and S2). For the four varieties studied,
the chlorophyll content was higher in plants treated with
increasing Cd concentrations than in the control plants.
The varieties with the highest mean chlorophyll content
were Reinette and CB502 (46.35 and 45.46, respectively),
followed by Plaisant (43.39) and Pedrezuela (37.21).
Different results were observed for the Cr treatments
(Table 7). First, we only recorded measurements for the
first two sampling periods because the plants had dried
out by the third period. The values for chlorophyll con-

Growth of Four Varieties of Barley (Hordeum vulgare L.) in Soils Contaminated with
Heavy Metals and Their Effects on Some Physiological Traits
1806
Table 5. Effect of different treatment of Zn on chlorophyll
content of four barley varieties.
Variety Treatment SPAD values Mean*
mM S1 S2 S3
CB502 0 45.3245.32 35.50 42.05 c
50 46.9550.30 37.88 45.04 b
150 49.4351.58 45.35 48.79 a
250 47.6051.38 44.08 47.69 a
Mean** 47.33 b49.65 a 40.70 c
Pedrezuela 0 44.3240.85 15.78 33.65 b
50 48.7245.93 7.93 34.19 ab
150 48.2546.07 14.67 36.33 a
250 50.6648.10 13.49 37.41 a
Mean** 47.98 a45.24 b 12.97 c
Reinette 0 46.7045.31 37.70 43.24 c
50 49.9352.63 45.22 49.26 a
150 48.0048.89 40.81 45.9 b
250 45.4245.66 37.92 43 c
Mean** 47.51 a48.12 a 40.41 b
Plaisant 0 40.6442.68 40.28 41.2 ab
50 44.4243.88 40.57 42.95 a
150 41.0441.01 35.97 39.34 b
250 44.6345.81 42.93 44.46 a
Mean** 42.69 a43.34 a 39.94 b
*Treatments followed by the same letter do not differ significantly (p < 0.5)
Duncan test; **Sampling followed by the same letter do not differ signifi-
cantly (p < 0.5) Duncan test.
Table 6. Effect of different treatments of Cd on chlorophyll
content of four barley varieties.
Variety Treatment SPAD values Mean*
mM S1 S2 S3
CB502 0 45.32 45.32 35.50 42.05 b
10 49.77 51.23 37.15 46.05 a
20 46.88 51.32 39.15 45.78 a
40 51.25 52.47 40.15 47.95 a
Mean** 48.31 a50.08 a 38.24 b
Pedrezuela 0 44.32 40.85 15.78 33.65 c
10 49.82 47.92 13.87 37.2 b
20 49.52 46.84 17.44 37.93 b
40 52.17 49.51 18.47 40.05 a
Mean** 48.95 a46.28 b 16.39 c
Reinette 0 46.70 45.31 37.70 43.24 c
10 47.90 50.51 43.86 47.42 ab
20 46.33 49.61 41.86 45.93 b
40 49.56 51.21 45.66 48.81 a
Mean** 47.62 a49.16 a 42.27 b
Plaisant 0 40.64 42.68 40.28 41.2 b
10 41.52 44.78 42.37 42.89 b
20 45.68 46.90 44.08 45.55 a
40 44.31 47.26 40.19 43.92 a
Mean** 43.04 b45.40 a 41.73 c
*Treatments followed by the same letter do not differ significantly (p < 0.5)
Duncan test; **Sampling followed by the same letter do not differ signifi-
cantly (p < 0.5) Duncan test.
Table 7. Effect of different treatments of Cr on chlorophyll
content of four barley varieties.
Variety TreatmentSPAD values SPAD valuesMean*
mM S1 S2
CB502 0 45.32 45.32 45.32 b
1 55.82 55.42 55.61 a
2 51.90 28.37 40.13 c
3 21.58 10.92 16.25 d
Mean** 43.65 a 35.06 b
Pedrezuela0 44.32 40.85 42.58 a
1 42.20 46.47 44.33 a
2 46.45 13.08 29.76 b
3 25.62 7.94 16.78 c
Mean** 39.64 a 27.08 b
Reinette 0 46.70 45.31 46.10 a
1 44.58 49.63 47.11 a
2 46.37 23.44 34.90 b
3 32.23 9.78 21.01 c
Mean** 42.47 a 32.04 b
Plaisant 0 45.64 42.68 44.16 a
1 46.03 40.20 48.12 a
2 46.32 39.26 42.79 b
3 19.78 9.78 14.78 c
Mean** 39.44 a 32.98 b
*Treatments followed by the same letter do not differ significantly (p < 0.5)
Duncan test; **Sampling followed by the same letter do not differ signifi-
cantly (p < 0.5) Duncan test.
tent obtained in the second sampling period were sig-
nificantly lower than the values measured during the first
period for all varieties studied. In contrast, when the Cr
concentration increased, the chlorophyll content was sig-
nificantly lower than in the control plants in the four va-
rieties studied.
It was evident that the mean values for the genotypes
followed the same trend for the Zn and Cd treatments,
although differences between the genotypes were smaller.
The CB502 variety demonstrated the highest chlorophyll
content (39.33), followed by Reinette (37.28), Plaisant
(37.46), and Pedrezuela (33.36). The differences were
significant only between the CB502 and Pedrezuela ge-
notypes.
3.4. Chlorophyll Fluorescence
In plants treated with different concentrations of Zn (Ta-
ble 8), chlorophyll fluorescence was similar across all
treatments. Between the sampling periods, the most im-
portant differences were between the first and final sam-
pling period, except for the Plaisant variety plants, where
no significant differences were recorded at any of the
sampling periods. The varieties with the highest mean

Growth of Four Varieties of Barley (Hordeum vulgare L.) in Soils Contaminated with
Heavy Metals and Their Effects on Some Physiological Traits 1807
Table 8. Effect of different treatments of Zn on chlorophy ll
fluorescence of four barley varieties.
Variety Treatment Fv/Fm Mean
mM S1 S2 S3
CB502 0 0.847 0.832 0.821 0.833 a
50 0.851 0.852 0.817 0.840 a
150 0.849 0.836 0.832 0.839 a
250 0.851 0.850 0.821 0.841 a
Mean** 0.849 a0.842 a 0.823 b
Pedrezuela 0 0.838 0.841 0.540 0.740 b
50 0.849 0.835 0.584 0.756 ab
150 0.843 0.834 0.650 0.775 a
250 0.845 0.838 0.653 0.779 a
Mean** 0.844 a0.837 a 0.607 b
Reinette 0 0.849 0.826 0.825 0.833 a
50 0.849 0.836 0.838 0.841 a
150 0.853 0.833 0.831 0.839 a
250 0.852 0.838 0.828 0.839 a
Mean** 0.850 a0.833 b 0.830 b
Plaisant 0 0.847 0.835 0.831 0.838 a
50 0.849 0.830 0.833 0.837 a
150 0.845 0.833 0.826 0.835 a
250 0.844 0.837 0.836 0.839 a
Mean** 0.846 a0.834 a 0.831 a
*Treatments followed by the same letter do not differ significantly (p < 0.5)
Duncan test; **Sampling followed by the same letter do not differ signifi-
cantly (p < 0.5) Duncan test.
Fv/Fm values were CB502 and Reinette (0.838), fol-
lowed by Plaisant (0.837) and Pedrezuela (0.763). There
were no differences recorded in chlorophyll fluorescence
among the different Zn concentrations tested. The Fv/Fm
values were lower during the third sampling period, ex-
cept for in the Plaisant variety plants, where no differ-
ences between periods appeared. The CB502 and Rei-
nette varieties had the highest mean Fv/Fm values (0.838),
followed by Plaisant (0.836) and Pedrezuela (0.763),
which had significantly lower values.
In Cd treatments (Table 9), the Fv/Fm values were
similar between the control plants and those treated with
the lowest metal concentrations, and these values were
significantly lower for plants treated with the highest
metal concentration for all genotypes tested. The only ex-
ceptions were in CB502 variety plants, where values for
Table 9. Effect of different treatments of Cd on chlorophyll
fluorescence of four barley varieties.
Variety Treatment Fv/Fm Mean*
mM S1 S2 S3
CB502 0 0.847 0.832 0.821 0.833 a
10 0.852 0.849 0.829 0.843 a
20 0.843 0.853 0.829 0.841 a
40 0.850 0.852 0.833 0.844 a
Mean** 0.848 a 0.846 a 0.827 b
Pedrezuela0 0.838 0.841 0.640 0.773 a
10 0.840 0.831 0.694 0.788 a
20 0.845 0.822 0.645 0.770 a
40 0.838 0.838 0.586 0.754 b
Mean** 0.840 a 0.832 a 0.616 b
Reinette 0 0.849 0.826 0.825 0.833 a
10 0.851 0.834 0.835 0.839 a
20 0.852 0.831 0.832 0.838 a
40 0.838 0.811 0.742 0.796 b
Mean** 0.847 a 0.825 b 0.808 b
Plaisant 0 0.847 0.835 0.831 0.837 a
10 0.842 0.840 0.840 0.840 a
20 0.842 0.845 0.831 0.842 a
40 0.841 0.839 0.767 0.815 b
Mean** 0.843 a 0.839 a 0.817 b
*Treatments followed by the same letter do not differ significantly (p < 0.5)
Duncan test; **Sampling followed by the same letter do not differ signifi-
cantly (p < 0.5) Duncan test.
the high concentration treatments did not differ from the
other three treatments. Across the sampling periods, the
most important differences were observed between the
first and the third periods. The varieties with the highest
mean Fv/Fm values were CB502, Reinette, and Plaisant
(0.840, 0.827, and 0.834, respectively). Pedrezuela dis-
played the lowest value (0.771). The Fv/Fm values in
plants treated with the highest Cd concentrations were
significantly lower relative to the other treatments, ex-
cept for the CB502 variety plants, in which it did not
differ from the other treatments. The last sampling period
recorded significantly lower values for the four varieties
studied. CB501, Plaisant, and Reinette displayed the
highest mean genotype values (0.840, 0.834, and 0.827,
respectively), and Pedrezuela had the lowest value
(0.771).

Growth of Four Varieties of Barley (Hordeum vulgare L.) in Soils Contaminated with
Heavy Metals and Their Effects on Some Physiological Traits
1808
As occurred with the chlorophyll content, the fluores-
cence also differed more in plants treated with different
concentrations of Cr (Table 10). In the four varieties
studied, the Fv/Fm values corresponding to the highest
metal concentration were significantly lower than those
in the control plants. The second sampling period also
had lower values than did the first period for the four
genotypes. The differences between the varieties were
small, with mean values of 0.806, 0.804, 0.793, and
0.779 for CB502, Reinette, Plaisant, and Pedrezuela,
respectively. This might be due to the more toxic effects
of Cr in plants, which highly affected the growth and
physiology of the plants treated with this metal.
The correlations between the SPAD values and FV/Fm
values were high in the three sampling periods (r = 0.79,
r = 0.89, and r = 0.77 for the first, second, and third pe-
riods, respectively; p < 0.001). The correlations between
the height and SPAD values (r = 0.72; p < 0.001), height
and Fv/Fm (r = 0.75; p < 0.001), dry weight and SPAD
values (r = 67; p < 0.001), and fluorescence and dry
weight values (r = 0.66; p < 0.001) were also significant.
Table 10. Effect of different treatments of Cr on chlorophyll
fluorescence of four barley varieties.
Variety Treatment Fv/Fm Mean*
mM S1 S2
CB502 0 0.847 0.832 0.839 a
1 0.852 0.845 0.848 a
2 0.855 0.755 0.804 b
3 0.743 0.720 0.731 c
Mean** 0.824 a 0.787 b
Pedrezuela 0 0.838 0.841 0.839 a
1 0.838 0.842 0.840 a
2 0.830 0.624 0.727 b
3 0.728 0.689 0.708 c
Mean** 0.808 a 0.748 b
Reinette 0 0.849 0.826 0.837 a
1 0.850 0.805 0.827 a
2 0.836 0.754 0.795 b
3 0.803 0.709 0.756 c
Mean** 0.834 a 0.773 b
Plaisant 0 0.847 0.835 0.841 a
1 0.838 0.849 0.843 a
2 0.829 0.747 0.788 b
3 0.792 0.610 0.701 c
Mean** 0.826 a 0.760 b
*Treatments followed by the same letter do not differ significantly (p < 0.5);
Duncan test; **Sampling followed by the same letter do not differ signifi-
cantly (p < 0.5) Duncan test.
4. Discussion
In higher plants, growth inhibition and reduction in bio-
mass production are considered to be responses to heavy
metal toxicity; therefore, height and dry weight are used
as indicators of toxicity [22]. The results obtained in this
study indicate that the barley varieties studied were more
sensitive to Cr treatments than to Zn or Cd treatments
(Figure 1). Treatment with Zn did not negatively affect
plant growth in the CB502 and Pedrezuela varieties, in-
cluding at the highest concentration levels. In the Cd
treatments, growth was somewhat reduced (i.e., 4% for
CB502 and 5% for Pedrezuela) when plants were treated
with the highest concentration levels. For the Reinette
and Plaisant varieties, the plants treated with the highest
concentrations of Zn grew 4% less than control plants,
and those treated with the higher concentration of Cd
grew 8% and 6% less than control plants. The low and
intermediate concentrations of Zn and Cd favored growth
and increased the dry weight of the shoots and roots in all
varieties of barley studied. Other studies have also dem-
onstrated that plant growth in some species can be sti-
mulated by high concentrations of Zn and other metals
[23,24]. One possible explanation is that these species
may have higher requirements of Zn and Cd than other
plant types. At the lowest Cr concentrations, growth was
reduced relative to the control plants, and at the highest
Cr concentrations, plant growth stopped at the flag leaf
stage (Figure 1). The toxic effect of Cr on growth and
biomass reduction has been previously demonstrated in
rice [25], in which tolerant varieties were identified, and
in Lolium [26], in which the physiological parameters
were also affected by Cr presence.
The dry weights were reduced in plants treated with Cr
compared to plants treated with Zn or Cd (Figure 2),
which indicates the lower tolerance to Cr in the studied
varieties. Differences were also observed between varie-
ties, with CB502 having the highest weights, followed by
Reinette, Plaisant, and Pedrezuela. Generally, the stress
produced by metals reduces plant growth due to a reduc-
tion in the chlorophyll content and the consequent inhibi-
tion of photosynthesis [22,27-29]. This fact is consistent
with our results because the mean chlorophyll content
and fluorescence values were higher for CB502 and Rei-
nette, followed by Plaisant and Pedrezuela, for all Zn, Cd,
and Cr treatments (Tables 5-10). The negative effect of
Cd and Cr on photosynthesis may be due to limitations in
mesophyll cells due to a reduction in both light efficiency
and the transport rate of electrons implicated in PSII, as
was demonstrated by Vasilev [12,30] in barley and by
Vernay [26] in Lolium. The results for Fv/Fm at the
highest metal concentration levels, which were signifi-
cantly lower for all varieties, are consistent with this ar-
gument.

Growth of Four Varieties of Barley (Hordeum vulgare L.) in Soils Contaminated with
Heavy Metals and Their Effects on Some Physiological Traits 1809
The amount of accumulated metal in the aerial parts
and the roots increased significantly with increasing me-
tal concentrations in the soil (Tables 2-4). Metal accu-
mulated preferentially in the root, and a significant rela-
tionship has been observed between the metal concentra-
tion applied to the soil and the concentration measured in
the roots and stems. This suggests that the root was the
first place to accumulate metal and that small amounts of
metal were translocated to the aerial part of the plant.
The greatest metal accumulation in roots and aerial parts
has been confirmed in species as different as Hordeum
vulgare [31], Triticum turgidum [19], Vicia faba [20],
Nicotiana tabacum [23], Eruca sativa [32], and Prunus
dulcis [28]. Following treatment with Zn or Cd, the geno-
types CB502, Plaisant, and Pedrezuela accumulated ap-
proximately twice the amount of metal in their roots rela-
tive to their aerial parts; however, Reinette accumulated
16-fold more Zn in the roots than in the aerial parts and
34-fold more Cd. These data indicate that the first three
genotypes have a mechanism of tolerance to Zn that al-
lows them to accumulate metal in their tissues without
affecting plant survival. Reinette seems to tolerate large
amounts of Zn and Cd, hindering the translocation of
these metals from the root to the aerial parts. In the Cr
treatments, slightly more than double the amount of me-
tal accumulated in the root relative to the aerial parts in
all genotypes except in Reinette, where twice the amount
of metal accumulated in the roots relative to the aerial
parts, which indicates the existence of more barriers to
metal transport towards the shoot in this variety.
In summary, the traits studied in barley displayed va-
riability, and this suggests the existence of two apparent
groups. CB502 and Reinette were most tolerant to the
concentrations of metals used in our trials because their
growth was least affected by metals and their chlorophyll
content and fluorescence values were higher relative to
the Pedrezuela and Plaisant varieties. The Plaisant vari-
ety plants accumulated greater amounts of Zn, Reinette
accumulated greater amounts of Cd, and CB502 accu-
mulated greater amounts of Cr. This is of great interest
when selecting a certain variety for phytoextraction in
contaminated soils because different plants will vary in
their tolerance and extraction capacity based on the type
of metal present in the soil.
REFERENCES
[1] A. J. M. Baker, S. P. McGrath, R. D. Reeves and J. A. C.
Smith, “Metal Hyperaccumulator Plants: A Review of the
Ecology and Physiology of a Biological Resource for
Phytoremediation of Metal-Populled Soils,” In: N. Terry
and G. Bañuelos, Ed., Phytoremediation of Contaminated
Soil and Water, CRP Press LLC, Boca Raton, 2000, pp.
85-107.
[2] S. P. McGrath, F. J. Zhao and E. Lombi, “Plant and
Rhizosphere Processes Involved in Phytoremediation of
Metal-Contaminated Soils,” Plant and Soil, Vol. 232, No.
1-2, 2001, pp. 207-214. doi:10.1023/A:1010358708525
[3] S. P. McGrath, F. J. Zhao and E. Lombi, “Phytoremedia-
tion of Metals, Metalloids, and Radionucleides,” Ad-
vances in Agronomy, Vol. 75, 2002, pp. 1-56.
doi:10.1016/S0065-2113(02)75002-5
[4] R. L. Chaney, “Plant Uptake of Inorganic Waste Con-
stituents,” In: J. F. Parr, P. B. Marsch and J. S. Kla, Eds.,
Land Treatment of Inorganic Wastes, Noyes Data, Park
Ridge, 1983, pp. 50-76.
[5] D. E. Salt, M. Blaylock, N. P. B. A. Kumar, V. Dushen-
kov, B. D. Ensley, I. Chet and I. Raskin, “Phytoremedia-
tion: A Novel Strategy for the Removal of Toxic Metals
from the Environment Using Plants,” BioTechnology, Vol.
13, No. 5, 1995, pp. 468-474. doi:10.1038/nbt0595-468
[6] S. D. Cunningham and D. W. Ow, “Promises and Pros-
pects of Phytoremediation,” Plant Physiology, Vol. 110,
No. 3, 1996, pp. 715-719.
[7] D. E. Salt, R. D. Smith and I. Raskin, “Phytoremedia-
tion,” Annual Review of Plant Physiology and Plant Mo-
lecular Biology, Vol. 49, No. 1, 1998, pp. 643-668.
doi:10.1146/annurev.arplant.49.1.643
[8] M. A. Soriano and E. Federes, “Use of Crops for in Situ
Phytoremediation of Polluted Soils Following a Toxic
Flood from a Mine Spill,” Plant and Soil, Vol. 256, No. 2,
2003, pp. 253-264. doi:10.1023/A:1026155423727
[9] C. W. A. Nascimento and B. Xing, “Phytoextraction: A
Review on Enhanced Metal Availability and Plant Ac-
cumulation,” Scientia Agricola, Vol. 63, No. 3, 2006, pp.
299-311. doi:10.1590/S0103-90162006000300014
[10] J. M. Clark, W. A. Norvell, F. R. Clark and W. T. Buck-
ley, “Concentration of Cadmium and Other Elements in
the Grain of Near-Isogenic Durum Lines,” Canadian
Journal of Animal Science, Vol. 82, No. 1, 2002, pp. 27-
33.
[11] D. Ueno, E. Koyama, N. Yamaji and J. F. Ma, “Physio-
logical, Genetic, and Molecular Characterization of a
High-Cd-Accumulating Rice Cultivar, Jarjan,” Journal of
Experimental Botany, Vol. 62, No. 7, 2011, pp. 2265-
2272. doi:10.1093/jxb/erq383
[12] A. Vassilev, J. Vangronsveld and I. Yordanov, “Cad-
mium Phytoextraction: Present State, Biological Back-
grounds and Research Needs,” Bulgarian Journal of
Plant Physiology, Vol. 28, No. 3-4, 2002, pp. 68-95.
[13] X. Zhang, G. Zhang, L. Guo, H. Wang, D. Zeng, G. Dong,
O. Qian and D. Xue, “Identification of Quantitative Trait
Loci for Cd and Zn Concentrations of Brown Rice Grown
in Cd-Polluted Soils,” Euphytica, Vol. 180, No. 2, 2011,
pp. 173-179. doi:10.1007/s10681-011-0346-9
[14] M. M. Lasat, “Phytoextraction of Metals from Contami-
nated Soil: A Review of Plant/Soil/Metal Interaction and
Assessment of Pertinent Agronomic Issues,” Journal of
Hazardous Substance Research, Vol. 2, No. 5, 2000, pp.
1-25.
[15] S. Kärenlampi, H. Schat, J. Vangronsveld, J. A. C. Verk-

Growth of Four Varieties of Barley (Hordeum vulgare L.) in Soils Contaminated with
Heavy Metals and Their Effects on Some Physiological Traits
1810
leij, D. van der Lelie, M. Mergeay and A. I. Tervahauta,
“Genetic Engineering in the Improvement of Plants for
Phytoremediation of Metal Polluted Soils,” Environmen-
tal Pollution, Vol. 107, 2000, pp. 225-231.
doi:10.1016/S0269-7491(99)00141-4
[16] M. R. Macnair, V. Bert, S. B. Huitson, P. Saumitou-La-
prade and D. Petit, “Zinc Tolerance and Hyperaccumula-
tion Are Genetically Independent Characters,” Proceed-
ings of the Royal Society B, Vol. 266, No. 1434, 1999, pp.
2175-2179. doi:10.1098/rspb.1999.0905
[17] N. Roosens, N. Verbruggen, P. Meerts, P. Ximénez-Em-
bún and J. A. C. Smith, “Natural Variation in Cadmium
Tolerance and Its Relationship to Metal Hyperaccumula-
tion for Seven Populations of Thlaspi caerulescens from
Western Europe,” Plant, Cell and Environment, Vol. 26,
No. 10, 2003, pp. 1657-1672.
doi:10.1046/j.1365-3040.2003.01084.x
[18] M. J. McLaughlin, D. R. Parker and J. M. Clarke, “Metals
and Micronutrients-Food Safety Issues,” Field Crops Re-
search, Vol. 60, No. 1, 1999, pp. 143-163.
doi:10.1016/S0378-4290(98)00137-3
[19] B. A. Adeniji, M. T. Budimir-Hussey and S. M. Macfie,
“Production of Organic Acids and Adsorption of Cd on
Roots of Durum Whea (Triticum turgidum L. var. Du-
rum),”Acta Physiologiae Plantarum, Vol. 32, 2010, pp.
1063-1072. doi:10.1007/s11738-010-0498-6
[20] R. Cabala, L. Slováková, M. El Zohri and H. Frank, “Ac-
cumulation and Translocation of Cd Metal and the Cd-
Induced Production of Glutathione and Phytochelatins in
Vicia faba L,” Acta Physiologiae Plantarum, Vol. 33, No.
4, 2011, pp. 1239-1248. doi:10.1007/s11738-010-0653-0
[21] J. C. Zadoks, T. T. Chang and C. F. Kozank, “A Decimal
Code for the Growth Stages of Cereals,” Weed Research,
Vol. 14, No. 6, 1974, pp. 415-421.
doi:10.1111/j.1365-3180.1974.tb01084.x
[22] D. Ci, D. Jiang, B. Wollenweber, T. Dai, Q. Jing and W.
Cao, “Cadmium Stress in Wheat Seedlings: Growth, Cad-
mium Accumulation and Photosynthesis,” Acta Phisiolo-
giae Plantarum, Vol. 32, No. 2, 2010, pp. 365-373.
doi:10.1007/s11738-009-0414-0
[23] L. L. Martins, M. P. Mourato, A. I. Cardoso, A. P. Pinto,
A. M. Mota, M. L. S. Goncalves and A. de Varennes,
“Oxidative Stress Induced by Cadmium in Nicotiana ta-
bacum L.: Effects on Growth Parameters, Oxidative Da-
mage and Antioxidant Responses in Different Plant
Parts,” Acta Physiologiae Plantarum, Vol. 33, 2011, pp.
1375-1383. doi:10.1007/s11738-010-0671-y
[24] Y. Yang, Ch. Sun, Y. Yao, Y. Zhang and V. Achal,
“Growth and Physiological Responses of Grape (Vitis vi-
nifera “Combier”) to Excess Zinc,” Acta Physiologiae
Plantarum, Vol. 33, No. 4, 2011, pp. 1483-1491.
doi:10.1007/s11738-010-0687-3
[25] B. Qiu, W. Zhou, D. Xue, F. Zeng, S. Ali and G. Zhang,
“Identification of Cr-Tolerance Lines in a Rice (Oryza
sativa L.) DH Population,” Euphytica, Vol. 174, No. 2,
2010, pp. 199-207. doi:10.1007/s10681-009-0115-1
[26] P. Vernay, C. Gauthier-Moussard and A. Hitmi, “Interac-
tion of Bioaccumulation of Heavy Metal Chromium with
Water Relation, Mineral Nutrition and Photosynthesis in
Developed Leaves of Lolium perenne L,” Chemosphere,
Vol. 68, No. 8, 2007, pp. 1563-1575.
doi:10.1016/j.chemosphere.2007.02.052
[27] L. M. Sandalio, H. C. Dalurzo, M. Gómez, M. C. Ro-
mero-Puertas and L. A. del Río, “Cadmium-Induced
Changes in the Growth and Oxidative Metabolism of Pea
Plants,” Journal of Experimental Botany, Vol. 52, 2010,
pp. 2115-2126.
[28] E. Nada, B. A. Ferjani, R. Ali, B. R. Bechir, M. Imed and
B. Makki, “Cadmium-Induced Growth Inhibition and Al-
teration of Biochemical Parameters in Almond Seedlings
Grown in Solution Culture,” Acta Physiologiae Plantta-
rum, Vol. 29, 2007, pp. 57-62.
doi:10.1007/s11738-006-0009-y
[29] R. W. dos Santos, E. C. Schmidt, R. Martins, A. Latini, M.
Maraschin, P. A. Horta and Z. L. Bouzon, “Effects of
Cadmium on Growth, Photosynthetic Pigments, Photo-
synthetic Performance, Biochemical Parameters and Struc-
ture of Chloroplasts in the Agarophyte Gracilaria domin-
gensis (Rhodophyta, Gracilariales),” American Journal of
Plant Sciences, Vol. 3, No. 8, 2012, pp. 1077-1084.
doi:10.4236/ajps.2012.38129
[30] A. Vassilev, I. Yordanov and T. Tsonev, “Effects of Cd2+
on the Physiological State and Photosynthetic Activity of
Young Barley Plants,” Photosynthetica, Vol. 34, No. 2,
1997, pp. 293-302. doi:10.1023/A:1006805010560
[31] A. González, V. Chumillas and M. C. Lobo, “Effect of Zn,
Cd and Cr on Growth, Water Status and Chlorophyll
Content of Barley Plants (H. vulgare L.),” Agricultural
Sciences, Vol. 3, No. 4, 2012, pp. 572-581.
doi:10.4236/as.2012.34069
[32] Y. Ozdener and B. K. Aydin, “The Effect of Zinc on the
Growth and Physiological and Biochemical Parameters in
Seedlings of Eruca sativa (L.) (Rocket),” Acta Physiolo-
giae Plantarum, Vol. 32, No. 3, 2010, pp. 469-476.
doi:10.1007/s11738-009-0423-z