Agriculture Reference
In-Depth Information
They were then washed with distilled water and sown on perlite imbibed with distilled water.
They remained in the dark, at room temperature for 7 days. The rooted cutting (
Sesuvium
) and
the seedlings (
Mesembryanthemum
) were transferred for 15 days on 1/10 Hewitt solution
supplemented with micronutrient and with 4.5 µM Fe in a glass house with mean
temperatures (night-day) of 18-25 °C and relative humidity 80-70%. Thereafter, the medium
was changed for non-diluted Hewitt solution, with micronutrients and 45 µM Fe plus 100 mM
NaCl (Basal medium (B)). For split root experiments, each plant was maintained between two
750 ml plastic containers filled with aerated solutions, with one half of the root system
plunging in each container.
Split-root experiment aimed at determining the implication of nutritional disruptions in
growth inhibition under heavy metals (Cd
2+
and Ni
2+
) stress. Five treatments were carried out
and schematized in Figure 1: In the first and second treatments, one half of roots were
immersed in basal medium, and the other half in the same medium supplemented with 100
µM Cd
2+
(B /Cd treatment) or 50 µM Ni
2+
(B/Ni treatment). In the others treatments, the two
halves of root system were immersed either in metal free basal medium (B/B) or in basal
medium with 100 µM Cd
2+
(Cd/Cd) or 50 µM Ni
2+
(Ni/Ni). The culture solution was renewed
weekly. Two harvests were made at the beginning of the treatment, and 30 days
later.
At the harvests, shoots were successively rinsed three times in cold water and blotted
between two layers of filter paper. Roots were dipped in a 0.01 M HCl cold solution to
eliminate any external heavy metals adsorbed at the root surface, then rinsed three times with
cold distilled water (Aldrich
et al.
2003) and blotted with filter-paper. The fresh weight was
immediately determined, and the dry one was measured after 48 hours of desiccation in an
oven at 60 °C.
Figure 1
.
schematic representation of different treatments used in this experiment. B: Basal medium; Cd
basal medium supplied with 100 µM Cd
2+
, Ni basal medium supplied with 50 µM Ni
2+
. For each
treatment, 8 replicates corresponding to single plants are used for both species.
Cation Analysis
Desiccated samples were grounded to a fine powder using a porcelain mortar and pestle,
then digested in 4/1 (v/v) HNO
3
/HClO
4
mixture. Cd, Ni, Ca and Fe concentrations were
determined by atomic absorption spectrometry (VARIAN, Spectra AA 220 FS). K
+
amounts
were determined in the same homogenate by flame spectrometry (Corning photometer).
