Figure 1.
Effect of 60 mM and 180 mM NaCl on the growth of six potato cultivars.
A. Diversity in the salt tolerance of 6 cultivars, shown as decreases in fresh weight after growth on hydroponic culture, relative to plant growth in the absence of NaCl. Results are means of three replicates and expressed as percentages from the weight of control plants. (±S.E.). The average coefficient of variation (CV) for all cultivars grown at 0 mM NaCl was 0.3 (0.2 to 0.4), for cultivars grown at 60 mM the CV was 0.4 (0.2 to 0.5) and for cultivars grown at 180 mM the CV was 0.5 (0.3 to 0.7). B. Representative photographs of the six potato cultivars grown on hydroponics for three weeks after treatment with either 0, 60 or 180 mM NaCl during the last seven days.
Figure 2.
Sodium and potassium concentrations in the leaves, stems and roots of the six cultivars.
Plants were grown hydroponically for three weeks and treated with either 0, 60 or 180 mM NaCl during the last seven days. At harvest, leaves, stems and roots were collected separately. Roots were rinsed with deionized water before analysis. Tissues were dried overnight at 70°C and Na+ and K+ contents in the tissue extracts were determined by using High Pressure Liquid Chromotography. Four plants in each treatment were used. The experiment was repeated three times and the results show the mean±SE.
Table 1.
K+:Na+ ratio calculated for leaf tissue of the six cultivar grown hydroponically for three weeks and treated with 60 or 180 mM NaCl.
Figure 3.
Plant tolerance index related to salinity tolerance and the sodium shoot distribution.
Relationship between (A) leaf, (B) stem and (C) root Na+ content and plant salinity tolerance, as measured by total fresh weight (FW) in salt stressed plants÷total FW in control plants (modified from Jha et al., 2010), in six potato cultivars. Results are the mean ± SE of three biological replicates. (D) Relationship (Shoot Distribution Index; SDI) between sodium concentrations in leaves and in stems, as determined by (sodium concentrations in leaves)÷(sodium concentrations in stems) for plants treated with 60 mM NaCl (x-axis) and plants treated with 180 mM NaCl (y-axis). The inserted dotted line represents the function y = (f)x. In both salt treatments, four cultivars have an SSD value of around one, what indicates that these four cultivars distribute sodium equally between leaves and stems. The SDI of Mozart and Mona Lisa reaches values of more than three after 60 mM NaCl treatment, what implies that sodium concentrations in the leaves are three times higher as compared to stems, after the 60 mM NaCl treatment.
Figure 4.
The effect of NaCl treatments on hydrogen peroxide concentrations in (A) leaves, (B) stems and (C) roots of six potato cultivars.
Data represents the means±SE for three biological replicates.
Figure 5.
The effect of NaCl treatments on proline concentrations in (A)leaves, (B) stems and (C) roots of six potato cultivars. Data represents the means±SE for three biological replicates.
Table 2.
Results of two way ANOVA of cultivar (C) and salinity (S) effects and their interaction (C×S) for the proline concentrations in leaf, stem and root tissues.
Figure 6.
Expression analysis of genes involved in the proline metabolism pathway.
The effect of NaCl treatments (0 and 60 mM) on the expression profile of P5CS1, P5CR, PDH, in the leaves (A, C, E) and the stems (B, D, F) of the cultivar Desiree and the cultivar Mozart. Results are the mean±SE for three biological replicates.
Table 3.
Selection of genes from the proline metabolism pathway.