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

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Z . Dajic
General inhibition of shoot growth with continued root growth has been considered
as a morphological adaptation to salt or water stress (Saab et al., 1990). An
increase of root/shoot ratio during the vegetation season was observed in the halophyte
Suaeda maritima, which might be a consequence of both ageing and increased
soil salinity (Dajic et al., 1997b).
6.1. Growth of Crops under Salt Stress
There are great varietal differences in plant growth responses to salinity, depending on
genotypic differences in rates of salt uptake, transport, accumulation and distribution
within the plant. For example, the shoot dry weight of three oat cultivars progressively
decreased under increasing concentrations of salinity (Dajic, unpublished data). The
most evident differences in growth responses to salinity were observed at the treatment
of 100 mM NaCl, whereas at higher salt concentrations a considerable reduction
of shoot dry weight (about three to five times lower at 150 mM and 300 mM, respectively,
than those of the control plants) occurred in all tested cultivars (Figure 4).
Figure 4. Growth reduction of oat cultivars (cv. Rajac, Slavuj and Lovcen) caused
by increasing salt concentrations
The salt tolerance of crop species, including cereals, forage crops, fruit crops
and vegetables (Table 3) is conventionally expressed (Maas and Hoffman, 1977) in
terms of relative yield (Y r
, i.e. the percentage of the yield of the crop grown under saline
conditions relative to that in non-saline conditions), threshold salinity value (a), that is,
the maximum soil salinity that does not reduce yields below those produced under nonsaline
conditions, and slope (b), the relative reduction per unit salinity increase from
threshold (soil salinity is expressed in terms of EC e
), as follows:
Y r
= 100 – b (Ec e
– a) (1)