conductance (gs) (Figure 2). Stomatal
conductance of plants irrigated with low
level of salinity (50 mM) decreased by 31%
compared with the controls. At high level of
salinity, stomatal conductance was very low
(91.3% decrease compared to the controls).
The ratio of intercellular to ambient CO2
concentration (Ci
:Ca) decreased up to 150
mM salinity compared to the controls
(Figure 3). In spite of decreasing ACO2 and gs
with increasing levels of salinity, the Ci:Ca
ratio not only showed no significant
reduction at 250 mM but also increased at
350 mM. In the control conditions, there was
no significant difference in Ci
:Ca
ratio
between the two cultivars.
Salinity and Leaf Ion Concentration
The concentration of salt in the rooting
medium induced a subtantial increase in Na+
concentration in leaves (P≤ 0.001) (Figure 4-
a). There were significant differences in leaf
sodium concentration between the two
cultivars at different levels of salinity.
Cultivar P29 had significantly higher Na+
content in its leaves at the lowest salinity (50
mM) than cv Madison (Figure 4-a).
However, at the highest salinity level, cv P29
had significantly lower leaf sodium content
compared to Madison. Leaf K+
concentration decreased significantly by
increasing salinity to around half of the
control values at 350 mM (Figure 3-b).
Choloride (Cl-
) contents in leaves of both
cultivars increased with increasing salt
concentration (Figure 3-c). There were no
significant differences in leaf Clconcentration
between the two cultivars in
the control plants. At high levels of salinity,
cv P29 had significantly lower Cl-
content in
leaves than Madison. There is substantial
evidence that accumulation of inorganic
ions, predominantly Na+
and Cl-
, has an
important role in the process of osmotic
adjustment. (Ashraf and Ahmad, 2000;
Ghoulam et al., 2002). The increase in Na+
and Cl-
concentrations in salinized expanded
leaves of the two cultivars was not similar.
Cultivar P29 (salt tolerant) accumulated less
Na+
and Cl-
in its cells at high levels of
salinity compared to cv Madison.
Schachtman and Munns (1992) reported that
lower rate of Na+
accumulation in expanding
leaves of Triticum species might be due to
higher leaf expansion and/or a mechanism
that limits the transport of roots uptake of
Na+
. The lower Na+
and Cl-
contents in P29 at
high levels of salinity could be attributed to
the higher rates of leaf expansion at high