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Seed germination is sensitive to salt stress. ABA and Ca2+ are involved in the regulation of seed germination under salt stress. Ca2+ influx mediated by glutamate receptors (GLRs) plays important roles in many physiological processes in plants. Here, we investigated the correlation of GLRs, Ca2+ and ABA during seed germination in response to salt stress by using Arabidopsis thaliana wild-type and T-DNA insertion knockout mutants of glutamate receptor homolog3.4. We demonstrated that atglr3.4-1 and atglr3.4-2 mutants were more sensitive to NaCl during seed germination and post-germination growth than wild-type plants. Treatments of wild-type seedlings with NaCl evoked a marked elevation in cytosolic CaCa2+ activity ([Ca2+]cyt), and the elevation was inhibited by antagonists of GLRs, while the NaCl-induced elevation in [Ca2+]cyt was impaired in atglr3.4-1 and atglr3.4-2 mutants. Moreover, the mutants exhibited a lower expression of SOS3, SOS2 and SOS1, and greater accumulation of Na+ than wild-type seeds in the presence of NaCl. Mutation of AtGLR3.4 rendered the mutants more sensitive to ABA, while overexpression of AtGLR3.4 made the transgenic lines more tolerant to ABA in terms of seed germination. However, there was no difference in ABA content between atglr3.4 mutants and wild-type seeds, accompanied by lower expression of ABI3 and ABI4 in atglr3.4 mutants when challenged with NaCl. These results demonstrate that AtGLR3.4-mediated Ca2+ influx may be involved in the regulation of seed germination under salt stress by modulating Na+ accumulation through the SOS pathway. [ABSTRACT FROM AUTHOR]

Seedlings ofS. robustuswere exposed to increasing NaCl concentrations (0, 50, 100, 150, 200, 250, and 300 mM) for 50, 100, and 150 days, in greenhouse conditions. Total dry weight and salt tolerance index decreased gradually with increasing NaCl concentrations. The optimum growth ofS. robustus(4.12 to 5.25 g · plant−1) was obtained between 0 and 150 mM at 150 days after salt stress. Foliar chlorophyll a and total chlorophyll contents increased with NaCl concentration at 50 days after treatment. There was no significant effect of salinity on chlorophyll a, b and total chlorophyll contents at 100 and 150 days after treatment. Higher Na contents were found in the shoots as compared to the roots. The Na content increased, while K decreased with increasing NaCl concentrations, suggesting competitive inhibition between absorptions of Na and K as a consequence, the K/Na ratios in shoots and roots decreased with increasing salinity. The proline contents inS. robustuswere more pronounced at 300 mM (2.02 µmol/g), 250 mM (2.64 µmol/g), and 200 mM NaCl concentrations (2.98 µmol/g) for 50, 100, and 150 days, respectively, as compared to the treatment without added NaCl. Overall,S. robustuscould be considered as salt tolerant on the basis of their performance in biomass production, accumulation of Na, similar foliar chlorophyll a, chlorophyll b and total chlorophyll contents, and accumulation of proline with increasing salinity. The potential ability ofS. robustusto accumulate significant amounts of Na makes this halophyte promising as a desalinization tool of salted soils. [ABSTRACT FROM AUTHOR]

Solanum scabrumMill. (huckleberry) is widespread in West, East and Central Africa, where it constitutes one of the most important leafy vegetables. However, the salinity tolerance of this crop has not yet been assessed. The objective of this study was to assess the response of huckleberry to salinity stress in comparison with eggplant (S. melongenaL.). Four-week-old seedlings of both species were subjected to two levels of salinity stress, 50 mM and 150 mM sodium chloride (NaCl), for 14 d. Leaf water potential of both species decreased with increasing salinity stress. This decrease was lower in huckleberry than in eggplant. Total dry weight and total leaf area were also decreased by salinity, and the reductions of total dry weight and total leaf area under the 50 mM treatment compared with the control were 25 and 18% in huckleberry, while they were 47 and 55% in eggplant, respectively. The increases in leaf sodium (Na) accumulation in the 50 and 150 mM treatments compared with the control were 65 and 66% for eggplant and 18 and 36% for huckleberry, respectively. Na accumulation in stem and root in huckleberry was higher than that of leaf, whereas it was the reverse in eggplant under both salinity treatments. Huckleberry accumulated less Na in the leaves than eggplant, suggesting that huckleberry might reduce the transport of Na to its leaves more effectively than eggplant. The decrease of potassium (K) accumulation and the increase of Na in leaves by salinity resulted in a higher Na/K ratio in leaves, but this trend was greater in eggplant than in huckleberry. The calcium (Ca) concentration in leaves of huckleberry was also increased by salinity, whereas that of eggplant was decreased. These results indicate that huckleberry is more tolerant to salinity than eggplant, and less decrease in leaf area associated with lower leaf Na and increased Ca concentrations may be important in enhancing quality and sustaining productivity of the crop under this stress. [ABSTRACT FROM PUBLISHER]

Two barley cultivars ( Hordeum vulgare L., cvs. Elo and Belogorskii) differing in salt tolerance were used to study Na uptake, expression of three isoforms of the Na/H antiporter HvNHX1-3, and the cellular localization of these isoforms in the elongation zone of seedling roots. During short (1 h) incubation, seedling roots of both cultivars accumulated approximately equal quantities of Na. However, after 24-h incubation the content of Na in roots of a salt-tolerant variety Elo was 40% lower than in roots of the susceptible variety Belogorskii. The content of Na accumulated in shoots of cv. Elo after 24-h incubation was 6.5 times lower than in shoots of cv. Belogorskii and it was 4 times lower after the salt stress treatment. The cytochemical examination revealed that three proteins HvNHX1-3 are co-localized in the same cells of almost all root tissues; these proteins were present in the tonoplast and prevacuolar vesicles. Western blot analysis of HvNHX1-3 has shown that the content of isoforms in vacuolar membranes increased in response to salt stress in seedling roots and shoots of both cultivars, although the increase was more pronounced in the tolerant cultivar. The content of HvNHX1 in the seedlings increased in parallel with the enhanced expression of HvNHX1, whereas the increase in HvNHX2 and HvNHX3 protein content was accompanied by only slight changes in expression of respective genes. The results provide evidence that salt tolerance of barley depends on plant ability to restrict Na transport from the root to the shoot and relies on regulatory pathways of HvNHX1-3 expression in roots and shoots during salt stress. [ABSTRACT FROM AUTHOR]