Investigating physiological and biochemical

 
Genotypes 
Chlorophyll ‘a’ (mg g
-1
 FW) 
Chlorophyll ‘b’ (mg g
-1
 FW) 
Chlorophyll a+b
Control 
NaCl
(100 mM) 
NaCl
(200 mM) 
Control 
NaCl
(100 mM) 
NaCl
(200 mM) 
Control 
NaCl
(100 mM) 
NaCl
(200 mM) 
S-907 
0.24± 0.12 
0.24±0.10
0.21±0.14
0.20± 0.09 
0.15±0.07
0.10±0.05
0.44± 0.09 
0.39±0.05
0.31±0.11
C-99-3-115 
0.24± 0.09 
0.24±0.08
0.22±0.10
0.20± 0.08 0.16±0.09
0.10±0.07
0.44± 0.12 
0.40±0.10
0.32±0.17
637-72 
0.24± 0.11 
0.24±0.14
0.23±0.09
0.22± 0.11 0.19±0.08
0.16±0.09
0.46± 0.12 
0.43±0.21
0.39±0.08
NO-303 
0.25± 0.10 0.24±0.09
0.23±0.06
0.23± 0.11 
0.19±0.09
0.16±0.07
0.48± 0.07 
0.43±0.05
0.39±0.06
Each value is an average of 3 replications ± SE 

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105 
3.3.3.3 Gas exchange
 
The data regarding plant stomatal conductance (g
s
) and photosynthetic rate (P
n
) in 
young leaves of linseed genotypes is shown in Table 3.3.3. Genotypes showed 
significant variations for their stomatal conductance and photosynthetic rate at all the 
levels of salt stress. The maximum stomatal conductance as well as photosynthetic 
rate was recorded in salt tolerant genotypes while the minimum stomatal conductance 
and photosynthetic rate was noted in salt sensitive genotypes. Stomatal conductance 
and photosynthetic rates of salt tolerant genotypes (637-72 and NO-303) was 
statistical with respect to salt sensitive genotypes C-99-3-115 and S-907 under control 
treatment. With the application of salts, a clear decline in Pn and gs was found in 
stressed plants of all the four linseed genotypes and this reduction was more 
prominent in salt sensitive genotypes than that in salt tolerant genotypes. At 100 mM 
NaCl, stomatal conductance changed from 1.93 to 1.57 mmol m
-2
s
-1
and 
photosynthetic rate reduced from 16.83 to 12.70 µmol CO
2
m
-2
s
-1
in genotype 637-72 
while these parameters reduced from 1.77 to 1.33 mmol m
-2
s
-1
and 16.50 to 11.93 
µmol CO
2
m
-2
s
-1
respectively in C-99-3-115 genotype. At 200 mM NaCl, stomatal 
conductance and photosynthetic rates of salt sensitive genotypes S-907 (0.50 mmol 
m
-2
s
-1
; 9.33 µmol CO
2
m
-2
s
-1
) and C-99-3-115 (0.57 mmol m
-2
s
-1
; 9.83 µmol CO
2
m
-2
s
-1
) were less than that of salt tolerant genotypes 637-72 (0.93 mmol m
-2
s
-1
; 10.93 
µmol CO
2
m
-2
s
-1
) and NO-303 (0.83 mmol m
-2
s
-1
; 10.87 µmol CO
2
m
-2
s
-1
) (Table 
3.3.3). Compared to control treatment, salt sensitive genotypes showed 74-75% 
stomatal conductance at 100 mM NaCl as compared to salt tolerant genotypes which 
showed 81.88% stomatal conductance at the same treatment. However, at 200 mM 
NaCl, stomatal conductance reduced more in salt sensitive genotypes (30-32% of 
control) rather than in salt tolerant genotypes (45-48%). Similarly, photosynthetic rate 
of salt sensitive genotypes reduced to 71-72% of respective control at 100 mM NaCl 
while in salt tolerant genotypes it was 75% of respective control at same salinity level 
while at 200 mM NaCl, photosynthetic rate was reduced to 57-60% in salt sensitive 
genotypes when compared with control but salt tolerant genotypes showed 65% 
photosynthetic rate of their respective control.

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106 
Table 3.3.3. Stomatal conductance (g
s
) and photosynthetic rate (P
n
) of linseed genotypes at different salinity levels