Agriculture Reference
In-Depth Information
Statistical Analysis
Analyses of variance (ANOVA) with orthogonal contrasts and mean comparison
procedures were used to detect differences between treatments. Mean separation procedures
were carried out using the multiple range tests with Fisher's least significant difference (LSD)
(P< 0.05).
R
ESULTS
Plant Morphology and Growth
After 15 days, chlorosis was visible on young leaves of
Sesuvium
plants subjected to
Cd/Cd and Ni/Ni treatments. Two weeks later, chlorosis was accentuated and other toxicity
symptoms, petiole necrosis and leaf fall, were evident in these plants.
Mesembryanthemum
plants submitted to Cd/Cd treatment showed a generalized chlorosis
;
while plants submitted
totally to Ni
2+
(Ni/Ni plants) showed a pronounced stunting. However, no visual toxicity
symptoms appeared in shoots of both species subjected to B/Cd and B/Ni treatments.
Globally, B/Cd and B/Ni treatments attenuated the toxicity symptoms found in Cd/Cd and
Ni/Ni plants.
Cd/Cd and Ni/Ni treatments reduced the shoot and the root dry matter production in both
species (Figure 2A, B) as compared to control (B/B). These effects were less marked (not
significant) for
Sesuvium
(Figure 2 A) and particularly pronounced in
Mesembryanthemum
(Figure 2 B). In
Sesuvuim
, B/Cd and B/Ni plants produced significantly more biomass than
B/B plants. In
Mesembryanthemum
, plants cultivated on dual medium (B/Ni and B/Cd),
produced a similar biomass when compared to control (B/B) and two fold of those produced
by Ni/Ni and Cd/Cd plants.
Cd
2+
Accumulation
In shoots, Cd
2+
accumulation differed between the two species. Accumulation in
Mesembryanthemum
shoots was twice of
Sesuvium
for both Cd/Cd and B/Cd treatments
(Figure 3A). In plants subjected to Cd/Cd treatment, Cd
2+
shoot-concentration reached 193
and 323 µg/g DW, respectively in
Sesuvium
and
Mesembryanthemum
and was higher than
those measured in B/Cd plants which attained 85 and 185µg/g DW respectively in
Sesuvium
and
Mesembryanthemum
. In spite of the alleviation of the Cd-effects on growth observed in
B/Cd plants as compared to Cd/Cd ones, the quantities of Cd
2+
deposited in shoots (Cd
2+
-
shoot concentration * shoot dry weight) in the two types of treatment were similar for each
species (Figure 3A). Thus the reduced Cd
2+
concentrations showed in the shoot of B/Cd
plants resulted from a dilution by growth.
In the root of both species, Cd
2+
was more accumulated than in the shoots. The root part
of B/Cd plants immersed in solution containing Cd
2+
and those of Cd/Cd showed the highest
Cd
2+
concentrations (Figure 3B). Moreover, the root part of B/Cd developed in Cd
2+
-free
