Ion homeostasis during salt stress in plants
Recent progress has been made in the characterization of cation transporters that maintain ion homeostasis during salt stress in plants. Sodium–proton antiporters at the vacuolar (NHX1) and plasma membrane (SOS1) have been identified in Arabidopsis. SOS1 is regulated by the calcium-activated protein kinase complex SOS2—SOS3. In yeast, a transcription repressor, Sko1, mediates regulation of the sodium-pump ENA1 gene by the Hog1 MAP kinase. The recent visualization at the atomic level of the inhibitory site of sodium in the known target Hal2 has helped identify the interactions determining Na+ toxicity.
Regulation of chlorophyll biosynthesis and degradation by salt stress in sunflower leaves
Helianthus annuus L. plants when exposed to increasing concentrations of NaCl showed a reduction of chlorophyll content and fluorescence (mainly due to a reduction of Fm). Chlorophyllase activity was higher in 15-day-old unstressed leaves. It increased during the first days in 25 mM NaCl stressed leaves decreasing with higher concentrations. NaCl effect on chlorophyll synthesis was then studied: only 50 and 100 mM NaCl inhibited synthesis of 5-aminolaevulinic acid, a precursor of chlorophyll. Our results show that: (1) chlorophyllase is stimulated during the first days in leaves under moderate stress but it is affected by high salt concentrations; (2) salt stress affects more drastically chlorophyll synthesis (decreasing ALA synthesis) than chlorophyllase-mediated degradation.
Microbial Models and Salt Stress Tolerance in Plants
Improving salt tolerance in crop plants remains an urgent issue in plant molecular biology. The adaptation of plants to NaCl involves metabolic reactions (synthesis of organic solutes) and transport phenomena (ion extrusion at the plasma membrane and vacuolar compartmentation). In addition, a plethora of salt-induced genes with a bewildering variety of suggested functions have been described. The uncertainties about the physiological roles and/or molecular bases of many of these phenomena make it difficult to select genes that could improve salt tolerance (halotolerance) in transgenic plants. We suggest that the field of salt tolerance can benefit by complementing the present phenomenological or descriptive approaches with a functional strategy directed toward isolating genes that, by overexpression of the corresponding protein, could improve salt tolerance. These halotolerance genes not only could illuminate the critical steps for salt tolerance, but also could provide the tools for improvement.
Exogenously Applied H2O2 Promotes Proline Accumulation, Water Relations, Photosynthetic Efficiency and Growth of Wheat (Triticum aestivum L.) Under Salt Stress
Aim: To determine the role of hydrogen peroxide (H2O2) in the alleviation of salt stress in wheat (Triticum aestivum L.).
Design of the Study: Wheat plants were grown with or without 100 mM NaCl and were treated with 0, 50 or 100 nM H2O2 treatments.
Place and Duration of Study: The experimental work was carried out in the naturally illuminated green house at the Department of Botany, Aligarh Muslim University, Aligarh, India between November to December, 2012.
Methodology: Plants were sampled at 30 days after seed sowing to determine physiological, biochemical and growth parameters.
Results: Treatment of plants with H2O2 significantly influenced the parameters both under non saline and salt stress. The application of both 50 and 100 nM H2O2 reduced the severity of salt stress through the reduction in Na+ and Cl- content; and the increase in proline content and N assimilation. This resulted in increased water relations, photosynthetic pigments and growth under salt stress. However, maximum alleviation of salt stress was noted with 100 nM H2O2 and 50 nM H2O2 proved less effective. Under non saline condition also application of H2O2 increased all the studied parameters.
Conclusion: The treatment of 100 nM H2O2 maximally benefitted the wheat plants under non saline condition and alleviated the effects of salt stress. The treatment of H2O2 increased proline content which might help increased photosynthetic pigments and growth under salt stress. The mechanism of proline metabolism by which H2O2 treatment may protect against salt stress will be investigated further.
Influence of Silicon and Nano-Silicon on Germination, Growth and Yield of Faba Bean (Vicia faba L.) Under Salt Stress Conditions
Aims: The present study was conducted to evaluate the effects of Silicon (Si) and Nano-Silicon (NSi) for ameliorating negative effects of salinity on germination, growth and yield of faba bean (Vicia faba L.).
Study Design: Factorial completely randomized design Pot experiments used with Si and NSi applied at 4 concentrations each (0, 1, 2 and 3 mM) and NaCl (0, 50, 100 and 200 mM) were studied.
Place and Duration of Study: Experiments were carried out in the greenhouse of Faculty of Science, Princess Nora Bint Abdulrahman University, Kingdom of Saudi Arabia during winter season of 2010/2011
Methodology: Si and NSi applied at 4 concentrations each (0, 1, 2 and 3 mM) and NaCl (0, 50, 100 and 200 mM) were studied. Germination characteristics such as germination percentage (GP), germination rate (GR) and mean germination time (MGT) were measured. Vegetative growth including plant height, leaf area and fresh and dry weights was also studied. Yield and its components were determined. Nutrient elements (N, P, K, Ca and Na) in the seeds were also determined.
Results: Results showed that salinity had deleterious effects on seed germination, plant growth and yield. N, P, Ca and K in seeds decreased at salinity stress but Na increased. Application of Si and NSiO2 significantly enhanced the characteristics of seed germination. Among the treatments, 2mM of Si or NSiO2 improved GP, GR and MGT. The harmful effect of salt stress on vegetative growth and relative water content (RWC) was also alleviated by the addition of Si and NSi which caused significant increases in plant height, fresh and dry weights, RWC and total yield. Seed quality, represented by nutrient elements, was also improved by application of Si and NSi.
Conclusion: It is concluded that the application of Si was beneficial in improving the salt tolerance of Vicia faba plants.
 Serrano, R. and Rodriguez-Navarro, A., 2001. Ion homeostasis during salt stress in plants. Current opinion in cell biology, 13(4), pp.399-404.
 Santos, C.V., 2004. Regulation of chlorophyll biosynthesis and degradation by salt stress in sunflower leaves. Scientia Horticulturae, 103(1), pp.93-99.
 Serrano, R. and Gaxiola, R., 1994. Microbial models and salt stress tolerance in plants. Critical Reviews in Plant Sciences, 13(2), pp.121-138.
 Ashfaque, F., R. Khan, M. I. and A. Khan, N. (2013) “Exogenously Applied H2O2 Promotes Proline Accumulation, Water Relations, Photosynthetic Efficiency and Growth of Wheat (Triticum aestivum L.) Under Salt Stress”, Annual Research & Review in Biology, 4(1), pp. 105-120. doi: 10.9734/ARRB/2014/5629.
 Abdul Qados, A. and Moftah, A. (2014) “Influence of Silicon and Nano-Silicon on Germination, Growth and Yield of Faba Bean (Vicia faba L.) Under Salt Stress Conditions”, Journal of Experimental Agriculture International, 5(6), pp. 509-524. doi: 10.9734/AJEA/2015/14109.