Abstract
Salinity is one of the major abiotic stress factors limiting plant growth and productivity. In the present study, the relationship between the source of N2 nutrition (biological N2 fixation or nitrate assimilation) and the resistance to salt stress in soybean plants grown as hydroponics in a growth chamber under controlled conditions was assessed. Part of the plants were inoculated by adding 108 cells ml-1 suspension of Bradyrhizobium japonicum strain 273 (nitrogen-fixing plants). The rest plants received N2 from the nutrient solution (nitrate-fed plants). Salt treatment was applied during the vegetative stage of growth (14 days from the onset of germination) by adding NaCl into the nutrient solution at concentrations of 40 mM and 80 mM. Analyses were performed on the 4th trifoliate leaf 14 days after salt treatment. Our results showed that compared with nitrate-fed plants, the nitrogen-fixing soybean plants had better water status, less affected electrolyte leakage indicating better membrane integrity, enhanced dry biomass, higher net photosynthetic rate, transpiration rate and stomatal conductance. The addition of 80mM NaCl increased the activity of glycolate oxidase (GO, E.C. 1.1.3.1) in leaves of nitrate-fed plants thus indicating enhanced photorespiration. In contrast, the enzyme activity measured in leaves of nitrogen-fixing soybean plants was found to decrease. Furthermore, when compared with the respective controls, the inhibition of both pigment and fresh biomass accumulation was less pronounced in the nitrogen-fixing plants. Thus, our results suggest that soybean plants with symbiotic N2 fixation are more resistant to salt stress and therefore, can be better adapted to high salinity than nitrate-fed plants.
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Claims 8
Claim · model-written summary
Nitrogen-fixing soybean plants had better water status than nitrate-fed plants under salt stress.
- Taxon
- soybean
Glycine maxe0 - Treatment
- nitrogen-fixing soybean plantse0
- Outcome
- water statuse1
- Direction
- bettere1
- Comparator
- nitrate-fed plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“compared with nitrate-fed plants, the nitrogen-fixing soybean plants had”
e1“better water status”
Claim · model-written summary
Nitrogen-fixing soybean plants had less affected electrolyte leakage, indicating better membrane integrity, than nitrate-fed plants.
- Taxon
- soybeanGlycine maxe0
- Treatment
- nitrogen-fixing soybean plantse0
- Outcome
- electrolyte leakagee1
- Direction
- less affectede1
- Comparator
- nitrate-fed plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“compared with nitrate-fed plants, the nitrogen-fixing soybean plants had”
e1“less affected electrolyte leakage”
Claim · model-written summary
Nitrogen-fixing soybean plants had enhanced dry biomass compared with nitrate-fed plants.
- Taxon
- soybeanGlycine maxe0
- Treatment
- nitrogen-fixing soybean plantse0
- Outcome
- dry biomasse1
- Direction
- enhancede1
- Comparator
- nitrate-fed plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“compared with nitrate-fed plants, the nitrogen-fixing soybean plants had”
e1“enhanced dry biomass”
Claim · model-written summary
Nitrogen-fixing soybean plants had higher net photosynthetic rate, transpiration rate and stomatal conductance than nitrate-fed plants.
- Taxon
- soybeanGlycine maxe0
- Treatment
- nitrogen-fixing soybean plantse0
- Outcome
- net photosynthetic rate, transpiration rate and stomatal conductancee1
- Direction
- highere1
- Comparator
- nitrate-fed plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“compared with nitrate-fed plants, the nitrogen-fixing soybean plants had”
e1“higher net photosynthetic rate, transpiration rate and stomatal conductance”
Claim · model-written summary
Adding 80 mM NaCl increased glycolate oxidase activity in leaves of nitrate-fed soybean plants, indicating enhanced photorespiration.
- Taxon
- nitrate-fed plantse0
- Organ / stage
- leavese0
- Treatment
- 80mM NaCle0
- Gene
- glycolate oxidasee0
- Outcome
- activity of glycolate oxidasee0
- Direction
- increasede0
Not reportedComparator
Verbatim
e0“The addition of 80mM NaCl increased the activity of glycolate oxidase (GO, E.C. 1.1.3.1) in leaves of nitrate-fed plants”
e1“indicating enhanced photorespiration”
Claim · model-written summary
Glycolate oxidase activity measured in leaves of nitrogen-fixing soybean plants decreased, in contrast to nitrate-fed plants.
- Taxon
- soybeanGlycine maxe0
- Organ / stage
- leavese0
- Outcome
- enzyme activitye0
- Direction
- decreasee0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the enzyme activity measured in leaves of nitrogen-fixing soybean plants was found to decrease”
Claim · model-written summary
Compared with the respective controls, the inhibition of pigment and fresh biomass accumulation was less pronounced in nitrogen-fixing soybean plants.
- Taxon
- nitrogen-fixing plantse0
- Outcome
- pigment and fresh biomass accumulatione0
- Direction
- less pronouncede0
- Comparator
- the respective controlse1
Not reportedTreatment
Verbatim
e0“the inhibition of both pigment and fresh biomass accumulation was less pronounced in the nitrogen-fixing plants”
e1“when compared with the respective controls”
Claim · model-written summary
The authors conclude that soybean plants with symbiotic N2 fixation are more resistant to salt stress than nitrate-fed plants.
- Taxon
- soybeanGlycine maxe0
- Treatment
- symbiotic N2 fixatione0
- Outcome
- resistant to salt stresse0
- Direction
- more resistante0
- Comparator
- nitrate-fed plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soybean plants with symbiotic N2 fixation are more resistant to salt stress and therefore, can be better adapted to high salinity than nitrate-fed plants”
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