The salinity condition in the plantroot zone prevents water uptake from soil by plants, because of the presence of osmotic potential in soilwaterdue to existence of salts, which finally, decreases transpiration of plants lead to decline crop yield. Once the soil isaffected by salts, soluble salts lower the osmotic potential of the soil water,making it more difficult for roots to remove water from the soil in requiredamount and rate to meet their evapotranspiration demand. This process affectthe plant water uptake even if the soil has sufficient quantity of water inroot zone ( Clark, 1990; Lamsalet al.
, 1999). Saltconcertation in soil solution reduces crop growth and yield by reducing the ability of plant roots toacquire water lead to nutrient deficiencies or toxicities ( Ganjegunteet al., 2008; Kravchik & Bernstein, 2013; Deinlein etal.
, 2014; Reddy etal., 2015). This is because water in principleflow from the high water potential (low salts in plant cells) to low potential(high salts in soils) or it flowing from less negative potential to morenegative potential which controlled by gradients in water potential. High soil salinity causes dehydration ofplant cells results in reduced plant growth and regularly death.
Dissolvedsalts cause dehydration of plant cells because the osmotic potential of soilwater is decreased. Therefore, plants cannot easily extract water from soils whensoil solutions have lower osmotic potentials than plant cells (Zhang, 2014).Tomaintain water uptake from a dry or saline soil, plants must decrease theirinternal water requirement below that of the soil water content. The degree to which plants can adjust to dryand saline conditions depends on their ability to balance a water need belowthat of the soil and their ability to tolerate high concentrations of NaClpresent in the root zone (Nemati et al., 2011; Reddy et al., 2015).
Salinity not only affects the final soil water content which plants canextract to, but also the rate at which they use water (Fujimaki et al., 2008).Therefore,it is very important to assess salinity stress on crop yield to see the extentof yield decrease under different salinity conditions.
Generally, crops aremost sensitive to salinity during root emergence and germination, some ofplants are most sensitive, some are resist, however the sensitivity of cropdepends on their growth characteristics and root system (Zhang, 2002). Toleranceto salinity may therefore involve variations in responses to each of thesefactors (Munns & Tester, 2008).