Physiology and Molecular Biology of Stress ... - KHAM PHA MOI

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the application of static and dynamic salinity stress indices (SSI) in order to determine
root zone salinity and ion flux to the shoot, respectively (Dalton et al., 1997), and the
separation of physical and biochemical processes governing plant salt tolerance (Dalton
et al., 2000).
The conceptual models, which do not neglect solute reactions in the root
zone, the surface evaporation and influence of immobile wetted pore space can accurately
predict the leaching requirements (Lr) for crops from salinity of irrigation water
and the crop salt tolerance threshold (Alsaeedi and Elprince, 1999). The application of
a sprinkler (such is triple line source sprinkler system) and a drip irrigation system was
successfully used in screening for salinity tolerance in barley (Isla et al., 1997). Several
other models dealing with estimation of specific parameters of soil salinity, two- and
three-dimensional equilibrium solute transport, field-scale spatial salinity patterns, etc.,
have been proposed during the last twenty years by USDA (USDA Salinity Laboratory,
http://www.ussl.ars.usda.gov/modelsmenu.htm). Among them, the newest model
(“WATSUIT”), developed in 2001, predicts the salinity, sodicity and the toxic solute
concentrations of the soil water within a simulated crop root zone. This model allows an
evaluation of crop salinity threshold, slope and yield at given salinity level. Nevertheless,
in case of increasing and variable salinity within farmer fields, an estimated yield
for the most of the cultivated species is far from acceptable. Hence, it seems that the
only reasonable option for utilization and management of highly salinized soils should
be domestication and use of halophytes.
13. POTENTIAL OF HALOPHYTES IN SALINE AGRICULTURE
For extremely salt-affected soils the use of halophytes is recommended (O’Leary, 1994),
since any attempt either of soil reclamation or introduction of genetically modified
crops, possibly adapted to such conditions, would be enormously expensive. Therefore,
the domestication of some of the more than 1500 species of halophytes quoted,
seems likely to be more successful and cheaper than the long-term process of modifying
and breeding of an existing crop to fit into the niche of halophytes (Flowers and
Yeo, 1995). Many halophytes have great potential for use in so called ”saline agriculture”,
i.e. as oil seeds, food, fodder, fuel, fiber and other products (Table 5), in addition
to their possible utilization in reclamation (phytoremediation) of highly salinized soils,
referred to previously.