Abstract
Salt stress has been demonstrated to trigger the overaccumulation of reactive oxygen species (ROS) within plant tissues. This process, in turn, has been shown to induce oxidative damage and further impair the physiological and metabolic processes. As a promising organic soil conditioner, biochar has proven effective in mitigating the adverse effects of salt stress in crops. Nevertheless, the synergistic and interactive effects of salt stress and biochar application on the osmotic adjustment system and antioxidant defense system of alfalfa (Medicago sativa L.) have not been fully elucidated. This study employed a completely randomized design, comprising four NaCl-induced salt stress levels (0, 3, 6, and 9 dS m−1) and three biochar application rates (0, 30, and 60 g kg−1). To evaluate the role and underlying mechanism of biochar in alleviating oxidative damage caused by salt stress in alfalfa, we determined the growth indicators (shoot biomass [SB], root biomass [RB], and total biomass [TB]), physiological indicators (total chlorophyll content and relative water content), and biochemical indicators (osmotic adjustment substances, antioxidant enzyme activities, and oxidative stress-related substances). Results indicated that salt stress significantly suppressed alfalfa biomass accumulation by 16%–84%. With increasing salt stress intensity, the contents of proline (Pro), glycine betaine (GB), soluble sugars (SS), and soluble proteins (SP), along with the activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), and polyphenol oxidase (PPO), significantly increased in alfalfa leaves; yet, these defensive responses failed to prevent the decrease in leaf relative water content and the significant accumulation of superoxide anion (O2•−), hydrogen peroxide (H2O2), and malondialdehyde (MDA) contents. These results indicated that the endogenous defense system alone is insufficient to counteract salt stress-induced oxidative damage. In contrast, compared with the non-biochar control, biochar application significantly increased alfalfa chlorophyll content (by ~40%) and biomass accumulation (by ~12%). Notably, under the 30 g kg−1 biochar treatment, the antioxidant enzyme activities and osmotic adjustment substance contents of alfalfa seedlings significantly decreased, accompanied by a marked reduction in O2•− (by ~13%), H2O2 (by ~21%), and MDA (by ~30%) contents. These results indicated that biochar could maintain the dynamic equilibrium of osmotic regulation and antioxidant enzyme systems in alfalfa leaves, and promote the synthesis of photosynthetic pigments and photosynthates, thereby enhancing alfalfa biomass accumulation by 54%–68%. However, under severe salt stress (9 dS m−1), excessive biochar application rate (60 g kg−1) failed to exert a positive effect on alfalfa growth, with only approximately a 1% increase in total biomass of alfalfa seedlings. Collectively, our findings demonstrated that appropriate biochar application can effectively alleviate salinity-induced oxidative damage in alfalfa and thus promote its growth in saline soils. To alleviate salt stress-induced phytotoxicity and optimize the efficacy of soil amendments, it is imperative to rationally regulate the application amount of biochar in saline soils.
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Claims 16
Claim · model-written summary
Salt stress significantly suppressed alfalfa biomass accumulation by 16%–84%.
- Taxon
- Medicago sativa
Medicago sativat0 - Treatment
- salt stresse1
- Outcome
- biomass accumulatione1
- Direction
- suppressede1
- Value
- 16%–84%e1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e1“Results indicated that salt stress significantly suppressed alfalfa biomass accumulation by 16%–84%”
Claim · model-written summary
With increasing salt stress intensity, proline, glycine betaine and soluble sugars increased in alfalfa leaves.
- Taxon
- Medicago sativaMedicago sativat0
- Organ / stage
- leavese2
- Treatment
- salt stress intensitye2
- Outcome
- proline (Pro), glycine betaine (GB), soluble sugars (SS)e2
- Direction
- increasede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e2“With increasing salt stress intensity, the contents of proline (Pro), glycine betaine (GB), soluble sugars (SS), and soluble proteins (SP), along with the activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), and polyphenol oxidase (PPO), significantly increased in alfalfa leaves”
Claim · model-written summary
With increasing salt stress intensity, soluble proteins increased in alfalfa leaves.
- Taxon
- Medicago sativaMedicago sativat0
- Organ / stage
- leavese2
- Treatment
- salt stress intensitye2
- Outcome
- soluble proteins (SP)e2
- Direction
- increasede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e2“With increasing salt stress intensity, the contents of proline (Pro), glycine betaine (GB), soluble sugars (SS), and soluble proteins (SP), along with the activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), and polyphenol oxidase (PPO), significantly increased in alfalfa leaves”
Claim · model-written summary
With increasing salt stress intensity, catalase, peroxidase and superoxide dismutase activities increased in alfalfa leaves.
- Taxon
- Medicago sativaMedicago sativat0
- Organ / stage
- leavese2
- Treatment
- salt stress intensitye2
- Outcome
- activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD)e2
- Direction
- increasede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e2“With increasing salt stress intensity, the contents of proline (Pro), glycine betaine (GB), soluble sugars (SS), and soluble proteins (SP), along with the activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), and polyphenol oxidase (PPO), significantly increased in alfalfa leaves”
Claim · model-written summary
With increasing salt stress intensity, ascorbate peroxidase and polyphenol oxidase activities increased in alfalfa leaves.
- Taxon
- Medicago sativaMedicago sativat0
- Organ / stage
- leavese2
- Treatment
- salt stress intensitye2
- Outcome
- ascorbate peroxidase (APX), and polyphenol oxidase (PPO)e2
- Direction
- increasede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e2“With increasing salt stress intensity, the contents of proline (Pro), glycine betaine (GB), soluble sugars (SS), and soluble proteins (SP), along with the activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), and polyphenol oxidase (PPO), significantly increased in alfalfa leaves”
Claim · model-written summary
The endogenous defence system alone is insufficient to counteract salt stress-induced oxidative damage in alfalfa.
- Taxon
- Medicago sativaMedicago sativat0
- Outcome
- counteract salt stress-induced oxidative damagee2
- Qualifier
- the endogenous defense system alone is insufficiente2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e2“the endogenous defense system alone is insufficient to counteract salt stress-induced oxidative damage”
Claim · model-written summary
Biochar application significantly increased alfalfa chlorophyll content by about 40% relative to the non-biochar control.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- biochar applicatione4
- Outcome
- chlorophyll contente4
- Direction
- increasede4
- Value
- ~40%e4
- Comparator
- non-biochar controle4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e4“compared with the non-biochar control, biochar application significantly increased alfalfa chlorophyll content (by ~40%) and biomass accumulation (by ~12%)”
Claim · model-written summary
Biochar application significantly increased alfalfa biomass accumulation by about 12% relative to the non-biochar control.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- biochar applicatione4
- Outcome
- biomass accumulatione4
- Direction
- increasede4
- Value
- ~12%e4
- Comparator
- non-biochar controle4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e4“compared with the non-biochar control, biochar application significantly increased alfalfa chlorophyll content (by ~40%) and biomass accumulation (by ~12%)”
Claim · model-written summary
Under 30 g kg-1 biochar, antioxidant enzyme activities and osmotic adjustment substance contents of alfalfa seedlings decreased significantly.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- 30 g kg−1 biochare5
- Outcome
- antioxidant enzyme activities and osmotic adjustment substance contentse5
- Direction
- decreasede5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e5“under the 30 g kg−1 biochar treatment, the antioxidant enzyme activities and osmotic adjustment substance contents of alfalfa seedlings significantly decreased”
Claim · model-written summary
Under 30 g kg-1 biochar, O2•− content decreased by about 13%.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- 30 g kg−1 biochare5
- Outcome
- O2•−e6
- Direction
- reductione6
- Value
- ~13%e6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e5“under the 30 g kg−1 biochar treatment, the antioxidant enzyme activities and osmotic adjustment substance contents of alfalfa seedlings significantly decreased”
e6“a marked reduction in O2•− (by ~13%), H2O2 (by ~21%), and MDA (by ~30%) contents”
Claim · model-written summary
Under 30 g kg-1 biochar, H2O2 content decreased by about 21%.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- 30 g kg−1 biochare5
- Outcome
- H2O2e6
- Direction
- reductione6
- Value
- ~21%e6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e5“under the 30 g kg−1 biochar treatment, the antioxidant enzyme activities and osmotic adjustment substance contents of alfalfa seedlings significantly decreased”
e6“a marked reduction in O2•− (by ~13%), H2O2 (by ~21%), and MDA (by ~30%) contents”
Claim · model-written summary
Under 30 g kg-1 biochar, MDA content decreased by about 30%.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- 30 g kg−1 biochare5
- Outcome
- MDAe6
- Direction
- reductione6
- Value
- ~30%e6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e5“under the 30 g kg−1 biochar treatment, the antioxidant enzyme activities and osmotic adjustment substance contents of alfalfa seedlings significantly decreased”
e6“a marked reduction in O2•− (by ~13%), H2O2 (by ~21%), and MDA (by ~30%) contents”
Claim · model-written summary
Biochar enhanced alfalfa biomass accumulation by 54%–68% under salt stress.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- biochare7
- Outcome
- alfalfa biomass accumulatione7
- Direction
- enhancinge7
- Value
- 54%–68%e7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e7“These results indicated that biochar could maintain the dynamic equilibrium of osmotic regulation and antioxidant enzyme systems in alfalfa leaves, and promote the synthesis of photosynthetic pigments and photosynthates, thereby enhancing alfalfa biomass accumulation by 54%–68%”
Claim · model-written summary
Biochar promotes synthesis of photosynthetic pigments and photosynthates in alfalfa.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- biochare7
- Outcome
- synthesis of photosynthetic pigments and photosynthatese7
- Qualifier
- maintain the dynamic equilibrium of osmotic regulation and antioxidant enzyme systemse7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e7“These results indicated that biochar could maintain the dynamic equilibrium of osmotic regulation and antioxidant enzyme systems in alfalfa leaves, and promote the synthesis of photosynthetic pigments and photosynthates, thereby enhancing alfalfa biomass accumulation by 54%–68%”
Claim · model-written summary
Under severe salt stress, 60 g kg-1 biochar gave only about a 1% increase in total biomass.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- 60 g kg−1e2
- Outcome
- total biomasse2
- Direction
- increasee2
- Value
- 1%e2
- Qualifier
- under severe salt stress (9 dS m−1)e2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e2“under severe salt stress (9 dS m−1), excessive biochar application rate (60 g kg−1) failed to exert a positive effect on alfalfa growth, with only approximately a 1% increase in total biomass of alfalfa seedlings”
Claim · model-written summary
Biochar application rate should be regulated rationally in saline soils.
- Taxon
- Medicago sativaMedicago sativat0
- Outcome
- application amount of biochare2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Responses of Osmotic Adjustment and Antioxidant Enzyme Activities in Alfalfa (Medicago sativa L.) Seedlings”
e2“it is imperative to rationally regulate the application amount of biochar in saline soils”
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