3.1 Growth attributes of camelina responses under the separate and combined effects of Si and Se under salinity stress
Recorded results of growth attributes, such as root-shoot length and their fresh as well as dry weight, indicate that the different treatments of silicon (Si) and selenium (Se) separately or in combination significantly (P ≥ 0.005) affected all growth attributes under SS conditions (Table 1). A graphical representation illustrates that SS significantly reduced the measured attributes of growth, such as shoot length, shoot fresh weight, shoot dry weight, root length, root fresh weight, and root dry weight in both camelina genotypes, Australian camelina, and Canadian camelina. The highest reduction of shoot length (9.00 cm), shoot fresh weight (11.2 g), shoot dry weight (3.01 g), root length (15.01 cm), root fresh weight (13.89 g), and root dry weight (2.87 g) were noted in Canadian camelina compared to Australian camelina under SS conditions ((Figure 1 a-f).
The different doses of Si and Se also significantly improved the measured growth characteristics of both camelina genotypes. The maximum shoot length (32.55 cm), shoot fresh weight (31.24 g), shoot dry weight (6.93 g), root length (38.91 cm), root fresh weight (33.15 g), and root dry weight (7.63 g) were recorded in the treatment where Si and Se were applied in combination (Si + Se @ 10 ppm and NaCl @ 100 ppm) compared to all other treatments in Australian camelina, while the lowest values of shoot length, shoot fresh weight, shoot dry weight, root length, root fresh weight, and root dry weight were noted in Canadian camelina under SS conditions (Figure 1 a-f).
Table 1: Analysis of variance table for growth parameters, leaf chlorophyll pigments, infrared gas analyzer attributes, biochemical, and antioxidant assays of camelina under s7alinity stress conditions
Measured attributes
|
Source of variance
|
Treatments (T)
|
Varieties (V)
|
T x V
|
Shoot length
|
369.77 ***
|
34.748 **
|
1.768 NS
|
Shoot fresh weight
|
11.915 ***
|
0.691 NS
|
0.115 NS
|
Shoot dry weight
|
248.401***
|
26.940**
|
0.497 NS
|
Root length
|
333.464 ***
|
42.563 **
|
0.348 NS
|
Root fresh weight
|
270.231 ***
|
19.520 **
|
0.974 NS
|
Root dry weight
|
15.294 ***
|
1.166 *
|
0.016 NS
|
Chlorophyll a content
|
0.361 ***
|
0.029 *
|
0.0010 NS
|
Chlorophyll b content
|
0.447 ***
|
0.030 *
|
0.0007 NS
|
Total chlorophyll content
|
1.603 ***
|
0.119 *
|
0.0024 NS
|
Carotenoids content
|
1.282 ***
|
0.102 **
|
0.0012 NS
|
Photosynthetic rate
|
118.31 ***
|
11.55 **
|
0.414 NS
|
Transpiration rate
|
6.2588 ***
|
0.8453 ***
|
0.0314 NS
|
Stomatal conductance
|
0.5262 ***
|
0.0060 **
|
0.00008 NS
|
Total proline
|
10155 ***
|
899.2 ***
|
15.6 NS
|
Total soluble sugar
|
5952.7***
|
525.29 **
|
23.09 NS
|
Total soluble protein
|
70.497 ***
|
3.763 **
|
0.162 NS
|
Total free amino-acid
|
555.09 ***
|
40.223 **
|
1.177 NS
|
APX
|
2.433 ***
|
0.243 **
|
0.0038 NS
|
CAT
|
11799 ***
|
1190.5 ***
|
36.2 NS
|
POD
|
13567 ***
|
1373.5 ***
|
29.2 NS
|
SOD
|
9258 ***
|
598.2 **
|
18.38 NS
|
***P ≤ 0.001, **P ≤ 0.01, *P ≤ 0.05; NS, non-signifcant
3.2 Leaf chlorophyll pigments of camelina responses under the separate and combined effects of Si and Se under salinity stress
Recorded results of leaf chlorophyll pigments, including chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid content, indicate that the different treatments of silicon (Si) and selenium (Se), separately or in combination, significantly (P ≥ 0.005) affected all leaf chlorophyll pigments under SS conditions (Table 1). A graphical representation illustrates that SS significantly reduced the measured attributes of chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid content in both camelina genotypes, (Australian camelina, and Canadian camelina). The highest reduction of chlorophyll a (0.89 mg/g FW), chlorophyll b (0.18 mg/g FW), total chlorophyll (1.07 mg/g FW), and carotenoid content (1.41 mg/g FW) was noted in Canadian camelina compared to Australian camelina under SS conditions (Figure 2 a-d).
The different doses of Si and Se also significantly improved both camelina genotypes' measured leaf chlorophyll pigments. The maximum chlorophyll a (1.69 mg/g FW), chlorophyll b (1.02 mg/g FW), total chlorophyll (2.71 mg/g FW), and carotenoid content (2.89 mg/g FW) were recorded in the treatment where Si and Se were applied in combination (Si + Se @ 10 ppm and NaCl @ 100 ppm) compared to all other treatments in Australian camelina. In contrast, the lowest values of chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid content were noted in Canadian camelina under SS conditions (Figure 2 a-d).
3.3 Gas exchange attributes of camelina responses under the separate and combined effect of Si and Se under salinity stress
All leaf gas exchange attributes under SS conditions were significantly (P ≥ 0.005) affected by the various treatments of silicon (Si) and selenium (Se), either separately or in combination, according to recorded results of gas exchange attributes, including photosynthetic rate, transpiration rate, and stomatal conductance (Table 1). A graphical depiction shows that in both camelina genotypes (Australian and Canadian), SS dramatically decreased the measured characteristics of photosynthetic rate, transpiration rate, and stomatal conductance. Under SS conditions, Canadian camelina showed the greatest drop in photosynthetic rate (3.54 µmol CO2 m-2 s-1), transpiration rate (0.48 µmol CO2 m-2 s-1), and stomatal conductance (0.09 µmol CO2 m-2 s-1) when compared to Australian camelina (Figure 3 a-c).
The assessed gas exchange properties of both camelina genotypes were significantly improved by the varied dosages of Si and Se. When Si and Se were applied together (Si + Se @ 10 ppm and NaCl @ 100 ppm), the maximum photosynthetic rate (17.02 µmol CO2 m-2 s-1), transpiration rate (3.65 µmol CO2 m-2 s-1), and stomatal conductance (0.38 µmol CO2 m-2 s-1) were recorded in Australian camelina as compared to all other treatments. On the other hand, under SS circumstances, Canadian camelina showed the lowest values of transpiration rate, stomatal conductance, and photosynthetic rate (Figure 3 a-c).
3.4 Biochemical characters of camelina responses under the separate and combined effect of Si and Se under salinity stress
Under SS conditions, all biochemical characters, including total proline, total soluble sugar, total soluble protein, and total free amino acid, showed significant (P ≥ 0.005) effects from the different treatments of silicon (Si) and selenium (Se), either separately or in combination (Table 1). A graphical representation demonstrates that SS significantly reduced the observed features of total proline, total soluble sugar, total soluble protein, and total free amino acid in both Australian and Canadian camelina genotypes. Comparing Canadian and Australian camelina under SS, the former displayed the largest declines in total proline (71.32 µmol/g DW), total soluble sugar (31.32 µmole/g FW), total soluble protein (1.79 mg/g DW), and total free amino acid (8.41 mg/g DW) were observed in Canadian camelina (Figure 4 a-d).
The different doses of Si and Se resulted in a significant improvement in the measured gas exchange characteristics of both camelina genotypes. In comparison to all other treatments, the maximum levels of total proline (195.15 µmol/g DW), total soluble sugar (120.95 µmole/g FW), total soluble protein (12.02 mg/g DW), and total free amino acid (37.15 mg/g DW) were recorded in Australian camelina when Si and Se were applied together (Si + Se @ 10 ppm and NaCl @ 100 ppm). Conversely, under SS conditions, total proline, total soluble sugar, total soluble protein, and total free amino acid values in Canadian camelina were the lowest (Figure 4 a-d).
3.5 Antioxidants assay of camelina responses under the separate and combined effects of Si and Se under salinity stress
Under SS circumstances, all antioxidant enzymes were significantly (P > 0.005) impacted by the various treatments of silicon (Si) and selenium (Se), either independently or in combination, according to recorded results of antioxidant activities, including APX, CAT, POD, and SOD (Table 1). A graphical depiction shows that in both camelina genotypes (Australian and Canadian), the SS dramatically decreased the observed characteristics of APX, CAT, POD, and SOD. When comparing Canadian camelina to Australian camelina under SS conditions, the greatest reductions in APX (1.95 Unit/min/g FW), CAT (29.36 Unit/min/g FW), POD (34.77 Unit/min/g FW), and SOD (126.42 Unit/min/g FW) were observed (Figure 5 a-d).
The measured leaf chlorophyll pigments of both camelina genotypes were significantly enhanced by the various dosages of Si and Se. When Si and Se were treated in combination (Si + Se @ 10 ppm and NaCl @ 100 ppm), the greatest APX (3.89 Unit/min/g FW), CAT (165.19 Unit/min/g FW), POD (178.95 Unit/min/g FW), and SOD (237.63 Unit/min/g FW) were reported in Australian camelina as compared to the other treatments. On the other hand, under SS circumstances, Canadian camelina showed the lowest values of APX, CAT, POD, and SOD (Figure 5 a-d).