The soil salinity condition in the soil
solution could affect plant growth directly due to its osmotic effect in soil
due to existence of salts, which finally decreases water flow in plants lead to decline crop
yield. Once the soil is affected 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 required amount and rate to meet their evapotranspiration
demand. This process further affect the plant water uptake even if the soil has
sufficient quantity of water in root zone ( Clark, 1990; Lamsal
et al., 1999).
other effect of salt concertation in soil is specific-ion effects which increase
certain ions concentration have a toxic characteristic on plant lead to reduce biochemical
process due to deficiencies or toxicities ( Ganjegunte et al., 2008; Kravchik
& Bernstein, 2013; Deinlein et al., 2014; Reddy et
al., 2015). This is because water in principle
flow 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 more
negative potential which controlled by gradients in water potential. High salinity concentration causes
dehydration of plant cells results in reduced plant growth and regularly cause wilting
in plant and finally death. This is due to low osmotic potential of soil water.
Therefore, plants cannot easily extract water from soils when soil solutions
have lower osmotic potentials than plant cells (Zhang, 2014).
maintain water uptake from a dry or saline soil, plants must decrease their
internal water requirement below that of the soil water content. The degree to which plants can adjust to dry
and saline conditions depends on their ability to balance a water need below and
their ability to tolerate high concentrations of NaCl present in the root zone (Nemati et al., 2011; Reddy et al., 2015). Salinity not only affects the final
soil water content which plants can extract to, but also the rate at which they
use water (Fujimaki et al., 2008).
it is very important to assess salinity stress on crop yield to see the extent
of yield decrease under different salinity conditions. Generally, crops are
most sensitive to salinity during root emergence and germination, some of
plants are most sensitive, some are resist, however the sensitivity of crop
depends on their growth characteristics and root system (Zhang, 2002). Tolerance
to salinity may therefore involve variations in responses to each of these
factors (Munns & Tester, 2008).