Dear Prosanta Kumar Dash for salt stress tolerance most important factors are, root architecture, longer roots take up more water, Relative water content improve water balance in plants less damaged caused by salt to cell, accumulation of osmolytes likes free proline, glycine betaine, soluble sugars etc.. and also accumulation of Potassium (K) will play an important role in stomatal conductance and ion balance in the cell.
One modifying method through transgenic approach, by overexpression of Na+/H+ antiporter of the vacuole. Basically, increasing number of pumps in vacuole plasma membrane to allow higher allocation of sodium inside the vacuole.
Soil salinization is a major threat to agriculture in arid and semi-arid regions, where water scarcity and inadequate drainage of irrigated lands severely reduce crop yield. Salt accumulation inhibits plant growth and reduces the ability to uptake water and nutrients, leading to osmotic or water-deficit stress. Salt is also causing injury of the young photosynthetic leaves and acceleration of their senescence, as the Na+ cation is toxic when accumulating in cell cytosol resulting in ionic imbalance and toxicity of transpiring leaves. To cope with salt stress, plants have evolved mainly two types of tolerance mechanisms based on either limiting the entry of salt by the roots, or controlling its concentration and distribution. Understanding the overall control of Na+ accumulation and functional studies of genes involved in transport processes, will provide a new opportunity to improve the salinity tolerance of plants relevant to food security in arid regions. A better understanding of these tolerance mechanisms can be used to breed crops with improved yield performance under salinity stress. Moreover, associations of cultures with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi could serve as an alternative and sustainable strategy to increase crop yields in salt-affected fields. According to standard definition, saline soils are those which have an electrical conductivity (EC) of the saturation soil-paste extract of more than 4 dS/m at 25°C, which corresponds to approximately 40 mM NaCl and generates an osmotic pressure of approximately 0.2 MPa . When grown on soils with an EC value above 4, crops significantly reduce their yield. Salts may include chlorides, sulfates, carbonates and bicarbonates of sodium, potassium, magnesium, and calcium, the diverse ionic composition of salt-affected soils results in a wide range of physiochemical properties. In the case of saline-sodic soils growth is hindered by a combination of high alkalinity, high Na+, and high salt concentration .. In this regard, it is important to distinguish between soil salinization and soil sodicity.
Soil salinization is referred as the accumulation of soluble salts in the soils .This is particularly favored by arid and semi-arid climates with evapotranspiration volumes being greater than precipitation volumes along the year.Soil sodicity is a term given to the amount of Na+ detained in the soil. High sodicity (more than 5% of Na+of the overall cation content) causes clay to swell excessively when wet, hence limiting severely air and water movements and resulting in poor drainage.Salts may arise naturally in subsoil (primary salinization) or maybe be introduced (secondary salinization) by soil amendments, inorganic fertilizers, and most importantly irrigation with brackish water. As a result, the total area of salt-affected lands in the world is estimated at more than 800 million hectares (ha), which account for more than 6% of the world’s total land area. Of the current 230 million ha of irrigated land, 45 million ha (19.5%) have been already damaged by salt.As NaCl is the most soluble and widespread salt, plants have evolved mechanisms to tolerate/exclude it while allowing acquisition of other nutrients available at low concentrations, such as phosphate, potassium, and nitrate.
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