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J. ENVIRON. SCI. HEALTH, A37(1), 71–84 (2002)
ROOT ZONE TEMPERATURE
AFFECTS THE PHYTOEXTRACTION
OF Ba, Cl, Sn, Pt, AND Rb USING
POTATO PLANTS (SOLANUM
TUBEROSUM L. VAR. SPUNTA)
IN THE FIELD
M. Baghour,1 D. A. Moreno,1 G. Vı´ llora,1
J. Hernandez,2 N. Castilla,3 and L. Romero1,*
´
1
Departamento de Biologı´ a Vegetal, Facultad de Ciencias,
Universidad de Granada, E-18071, Granada, Spain
2
Departamento de Biologia Vegetal, EUP Ingenierı´ a
´
Tecnica Agrı´ cola, 04120 Almerı´ a, Spain
3
Departamento de Horticultura, CIFA, Camino de
Purchil s/n, 18004 Granada, Spain
ABSTRACT
Three consecutive years of field experiments were conducted to investi-
gate how different root-zone temperatures, manipulated by using differ-
ent mulches, affect the phytoextraction of Ba, Cl, Sn, Pt and Rb in
different organs of potato plants (roots, tubers, stems and leaves). Four
different plastic covers were used (T1: transparent polyethylene; T2: white
polyethylene; T3: white and black coextruded polyethylene, and T4:
black polyethylene), using uncovered plants as control (T0). The different
treatments had a significant effect on mean root zone temperatures
(T0 ¼ 16 C, T1 ¼ 20 C, T2 ¼ 23 C, T3 ¼ 27 C and T4 ¼ 30 C) and
induced a significantly different response in Ba, Cl, Sn, Pt and Rb con-
centration and accumulation. The T3 treatment gave rise to the greatest
phytoextraction of Ba, Pt, Cl and Sn in the roots, leaflets and tubers.
*Corresponding author. E-mail: [email protected]
71
Copyright # 2002 by Marcel Dekker, Inc. www.dekker.com
ORDER REPRINTS
72 BAGHOUR ET AL.
In terms of the relative distribution of the phytoaccumulated elements
(as percentage of the total within the plant), Pt and Ba accumulated
mainly in the roots whereas Rb, Sn and Cl accumulated primarily in
tubers, establishing a close relationship between the biomass develop-
ment of each organ and phytoaccumulation capacity of metals in
response to temperature in the root zone.
Key Words: Solanum tuberosum L.; Mulching; Phytoextraction; Root-
zone temperature
INTRODUCTION
There are several elemental pollutants which are considered to be
potential threats to environmental systems (1), and are currently found
in soil and water pollution, provoking serious problems for human health.
This pollution could be alleviated with the application of phytoremediation
technologies (2,3). Recently, the use of plants to extract heavy metals from soil
(phytoextraction) has received much attention due to the possibility
of decontaminating some currently polluted soils (Phytoremediation), by
growing plants in soil containing elevated concentration of pollutants
having a large biomass production and thus not dangerously high concentra-
tions of elements in harvestable portion (4). This is a newly evolving field of
science and technology using plants to clean-up polluted soils, waters, or air
(5,6), and is a particularly important because contaminated soils are often used
for vegetable production. A technique that has strongly boosted agricultural
output in the last few years is the use of plastic covers over the soil surface
which significantly influences the root zone temperatures (7), depending on the
composition of the plastic as well as its efficiency in absorbing light (8,9). Root-
zone temperature is a key factor in altering ion accumulation (10). Given that
phytoextraction requires plants of high biomass production the objective of
this study was to determine how root zone temperatures generated under
plastic mulches determines the Ba, Cl, Sn, Pt, and Rb extraction in field
grown potato plants in order to evaluate the technique for phytoextraction.
MATERIALS AND METHODS
Crop Design
The experiment was conducted for three consecutive years (1993, 1994
and 1995) in the field (Granada, Spain), using Solanum tuberosum L. var.
Spunta, planted at the beginning of March and the crop cycle was about 4
months. The climate was semiarid and the area intensively used for agricul-
ture. The soil used showed the following characteristics: 45.3% silt, 43.2%
and clay 11.2%, pH (H2O 1 : 2.5) 8.6; electrical conductivity 1.10 dS mÀ1,
ORDER REPRINTS
ROOT ZONE TEMPERATURE AND PHYTOEXTRACTION 73
CaCO3 11.2%; total N (0.1%); P2O5 (58 mg gÀ1); K2O (115 mg gÀ1);
DTPA þ TEA þ CaCl2 (pH 7.3) extractable Ba (5.1 mg kgÀ1), Sn and Pt
(58 mg kgÀ1) and Rb (12 mg kgÀ1); ClÀ in satured extract (218 mg kgÀ1). The
characteristics of the irrigation water were: pH 7.6; E.C. 1.05 dS mÀ1; ClÀ
58 mg LÀ1; Naþ 25 mg LÀ1; Kþ 4 mg LÀ1; H2CO3 369 mg LÀ1, Ba 29 mg LÀ1;
Cl 35 mg LÀ1, Sn and Pt 1 mg LÀ1, Rb 2 mg LÀ1.
The experimental design was a factorial arrangement in a randomized
complete block with 5 treatments replicated 4 times (20 plots). Each plot
occupied an area of 78.4 m2, with a planting density of 4.2 plants mÀ2.
Plants were spaced 30 cm apart, with 80 cm between rows. The soil tempera-
ture was measured at the 15-cm in depth, using probes (107 type) from
Campbell Scientific TM. Root zone temperature was measured (6 measure-
ments at 4-h intervals) every 3 days of the crop cycle.
The different treatments consisted of covering the soil surface of each
plot with plastic mulches (polyethylene sheets), making a tight seal with the
soil: transparent polyethylene (25 mm in thickness, T1), white polyethylene
(25 mm in thickness, T2), coextruded black and white polyethylene (50 mm in
thickness, T3), and black polyethylene (25 mm in thickness, T4). Finally, no
plastic was applied in the control treatment (T0).
The fertilization used was the same as is habitually applied by farmers in
the zone. In the month of February in all three years, N (NH4NO3) and P and
K (K2HPO4) were applied (27 g mÀ2). Afterwards, at the end of the month of
April, 25 g mÀ2 of NH4NO3 were applied. Fertigation was complemented with
the following micronutrients: Fe: 0.5 mg LÀ1; B: 0.1 mg LÀ1; Mn: 0.1 mg LÀ1;
Zn: 0.075 mg LÀ1; Cu: 0.075 mg LÀ1 and Mo: 0.05 mg LÀ1. Iron was applied as
FeEDDHA, B as H3BO3 and the remaining micronutrients as sulphates.
Plant Sampling
The plant material (stems, leaves, roots and tubers) were sampled 6
times every two weeks, throughout the plant development for the three
years of experiments. For each sampling, 10 plants were collected from
each replicate per treatment. Leaf samples were taken only from plants
with fully expanded leaves of the same size. Leaves were picked at about
one third of the plant height from the plant apex. Roots, leaves, stems and
tubers were rinsed three times in distilled water after decontamination with
non-ionic detergent at 1% (11), then blotted on filter paper. Then a sample
was dried in a forced air oven at 70 C for 24 h, ground in a wiley mill and
then placed in plastic bags for the further analyses.
Plant Analysis
For the assay of total Ba, Sn, Pt and Rb concentrations, oven-dried at

70 C for 24 h and pulverized plant material was digested with concentrated
ORDER REPRINTS
74 BAGHOUR ET AL.
nitric acid and measures were carried out by using an atomic absorption
spectrophotometer equipped with a graphite furnace (12). Reagent blanks
for analysis were also prepared performing the entire extraction procedure
but in the absence of the samples. For the soluble Ba, Sn, Pt and Rb deter-
mination, dry matter (0.15 g) was extracted with 10 mL 1 M HCl for 30 min
and then filtered, and determined using the method indicated above. Reagent
blanks for both analysis were also prepared performing the entire extraction
procedure but in the absence of the samples.
ClÀ was determined in an aqueous extract (13) by titration with AgNO3
according to the procedure of Kolthoff and Kuroda (14).
Statistical Analysis
All data were subjected to an analysis of variance and the mean of
separation according to the Duncan’s Multiple Range Test was represented
with lowercase letters. Levels of significance for the correlation analysis
were represented as follows: ***p


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