Environmental Engineering Reference
In-Depth Information
2.7. Measurements of Net Na
+
, H
+
and Cl
-
Fluxes
The net fluxes of Na
+
, K
+
, H
+
, and Cl
-
were carried out by Non-invasive Micro-test
Technique (NMT-YG-100, Younger, USA). The principle of the measurement was that the
ion fluxes were calculated from the ion specific PD (potential difference) between two points.
The glass micropipettes which were pepulled and silanized in advance were filled with a
backfilling solution (Na
+
: 100mM NaCl; K
+
: 100mM KCl; H
+
: 40mM KH
2
PO
4
+15mM NaCl;
Cl
-
: 100mM KCl) to a length of approximately 1cm. Then the micropipettes were filled with
selective liquid ion-exchange cocktails and an Ag/AgCl wire electrode holder was inserted in
the micropipettes.
Ion-selective electrodes were firstly calibrated before the flux measurements. The
concentrations of the calibrator were as follows: (1) Na
+
: 5mM, 2mM, 1mM (2mM in
measuring solution); (2) K
+
: 1mM, 0.5mM, 0.1mM (0.5mM in measuring solution); (3) H
+
:
pH5, 6, 7 (6 in measuring solution); (4) Cl
-
: 2mM, 0.5mM, 0.25mM (0.5mM in measuring
solution). Only electrodes with Nernstian slopes >50mV/decade (<-50mV/decade for Cl
-
electrodes) were used.
The root apexes at the length of 3 cm fastened to the bottom of measuring dish, washed
with the deionized water and incubated immediately in the measuring solution for 20 min.
The measuring sites located at 500µm from the root apex. The measuring solution were as
follows: (1) Na
+
: 0.1mM KCl, 0.1mM CaCl
2
, 0.1mM MgCl
2
, 2mM NaCl, 0.3 mM MES, pH
6.0, adjusted with choline and HCl; (2) K
+
: 0.1mM KCl, 0.1mM CaCl
2
, 0.1mM MgCl
2
, 0.3
mM MES, pH 6.0, adjusted with choline and HCl; (3) H
+
: 0.1mM KCl, 0.1mM CaCl
2
,
0.1mM MgCl
2
, 0.3 mM MES, pH 6.0, adjusted with NaOH and HCl; (4) Cl
-
: 0.05mM KCl,
0.05mM CaCl
2
, 0.05mM MgCl
2
, 0.25mM NaCl, pH 6.0, adjusted with choline and H
3
PO
3
.
Ultimately, the miro-volts differences were converted into net ion fluxes with the help of the
software JCal V3.0 (Xuyue Sci. and Tech., China).
2.8. Statistical Analysis
All the data in this study were analyzed by Microsoft Excel 2007, and moreover, the one-
way ANOVA was performed by adopting SPSS computer package (SPSS Inc., USA). Every
data acquired in the experiments is the mean of three biological replications at least.
Significant differences between means were determined through LSD test. Differences were
considered statistically significant when P < 0.05. All data were presented as mean ±SD. In
addition, the Figures were all created with SigmaPlot 10.0 (Systat Software, Inc. Germany).
3.
R
ESULTS
3.1. The Effects of NaCl on Water Potential (ψ
w
)
and Relative Water Content (RWC)
Just as we mentioned above, the water balance of the whole-plant would be disturbed
primarily no matter under salt or drought stresses. The high concentration ions in the soil
