Agriculture Reference
In-Depth Information
Table 1. Changes in the RGR (Relative Growth Rate) of
S. portulacastrum
and
M.
crystallinum
exposed during 30 days to different treatments. RGR measures the
quantity of biomass deposited by 1 g of biomass per unit of time. It was estimated as
Δln(DW)/Δt, where DW is the dry weight, ln stands for natural logarithm and Δ
represents the difference between final and initial value (Hunt, 1990). Means of 8
replicates. Values marked with same letter are not significantly different at p= 0.05
RGR (d
-1
)
M. crystallinum
Treatments
S. portulacastrum
B/B
B/Cd
B/Ni
Cd/Cd
Ni/Ni
0.097 ± 0.01(b)
0.082 ± 0.012(b)
0.096 ± 0.006(b)
0.06 ± 0.015(a)
0.06 ± 0.005(a)
0.06 ± 0.01(b)
0.07 ± 0.003(c)
0.07 ± 0.01(c)
0.05 ± 0.01(a)
0.05 ± 0.01(a)
Table 2. Changes in K
+
(mmol plant
-1
), Ca
2+
(mmol plant
-1
) and Fe (µmol plant
-1
)
amounts accumulated in the shoots of
S. portulacastrum
and
M. crystallinum
submitted
to different heavy metals treatments. Means of 8 replicates. Values marked with same
letter are not significantly different at p= 0.05.
S. portulacastrum
B/B
B/Cd
B/Ni
Cd/Cd
Ni/Ni
Element
K (mmol)
1.66 ± 0.5(b)
2.06 ± 0.2 (cb)
2.26 ± 0.2 (c)
0.86± 0.15(a)
0.87 ± 0.16(a)
Ca (mmol)
0.67 ± 0.2 (a)
1.13 ± 0.2 (b)
0.72 ± 0.22(a)
0.56 ± 0.1(a)
0.48 ± 0.09(a)
Fe (µmol)
8.14 ± 3(dc)
13.21 ± 3.2(ef )
7.5 ± 0.9(bc)
2.75 ± 0.5(a)
5.35 ± 1(ab)
M. crystallinum
B/B
B/Cd
B/Ni
Cd/Cd
Ni/Ni
K (mmol
5.9 ± 1.2(c)
3.56 ± 1.1 (b)
4.44 ± 1.1 (cb)
0.86 ± 0.3 (a)
0.813 ± 0.1(a)
Ca (mmol
0.33 ± 0.09(c)
0.27± 0.06(bc)
0.52 ± 0.04 (d)
0.14 ±
0.03(ab)
0.08 ± 0.01 (a)
Fe (µmol)
22.35 ± 4.5(g)
10.7± 3.2(de)
17.6 ± 2.5(fg)
3.32 ± 0.5 (ab)
2.32 ± 0.3 (a)
Indeed, one of the known toxic effects of heavy metals on plant physiology is the
alteration of the water balance, which is probably due to damages caused to membrane
integrity, turgor potential and cell wall elasticity (Barcelo and Poschenrieder, 1990, Perfus-
Barbeoch
et al.
2002). Some of our data support the depression action of Cd
2+
and Ni
2+
on
cellular turgor, when plants were cultivated completely in the presence of Cd
2+
(Cd/Cd) or
Ni
2+
(Ni/Ni). Plants showed shoot dehydration in both halophytes (not shown). However,
split-root system treatments restored adequate shoot water provisioning, demonstrating that
the half of root system grown in free metal medium is able to provide sufficient water to
sustain the whole plant growth and thus mitigated the effects of absorbed metal ensured by
the other half.
On the other hand, excepting few hyperaccumulators species which are able to
accumulate toxic heavy metals in the shoots at relatively high concentrations without growth
reduction, other species can not survive even at very low toxic metals levels accumulation in
