Abstract:
A factorial pot experiment based on randomized comp
lete blocks design with four
replications was carried out in order to evaluate s
alt tolerance of four sugar beet cultivars
including Madison (British origin) and three Irania
n cultivars (7233-P
12
, 7233-P
21
and
7233-P
29
) using carbon isotope discrimination (
∆
). Plants were grown in sand culture
medium in greenhouse conditions. Sugar beet cultiva
rs were irrigated with saline water
(tap water as control, 50, 150, 250 and 350 mM of N
aCl and CaCl
2
in 5: 1 molar ratio)
from 4-leaf stage for 16 weeks. Carbon isotope disc
rimination significantly decreased with
increasing salinity. Significant differences of
∆
between shoot and root were observed in
all cultivars and all levels of salinity. Madison
cv.
showed lower
∆
in shoot and root than
the other three cultivars at all levels of salinity
except the control, but
cv
. 7233-P
29
had
significantly higher
∆
values at saline conditions of 150 mM and above. A
lthough the
regression of
∆
and
C
i
/C
a
was
positive, the slope of regression line was differen
t from the
pattern predicted by theory, indicating an underest
imation of
∆
in these samples.
Relatively higher
13
C (lower
∆
) was found in root as compared with shoots.
Keywords
: Carbon/ Nitrogen ratio, Photosynthesis, Salt stre
ss, Stomatal conductance, Water
use efficiency.
