Abstract
Abiotic stresses, including nitrogen stress (NS), can hamper photosynthesis and cause oxidative damage to plants. Upregulation of the antioxidative defense system and photosynthesis induced by exogenous glycinebetaine (GB) and humic acid (HA) can mitigate the inhibitory effects of NS on plants. In the present investigation, the beneficial effects of exogenously applied GB and HA were examined on growth, leaf N status, photosynthesis, lipid peroxidation, and activities of some key antioxidant enzymes in the seedlings of maize cv. Zhengdan 958 (ZD958) exposed to NS. NS caused a significant reduction in total dry matter of seedlings of ZD958, but both GB and HA proved effective in mitigating this inhibition, hence, the beneficial effects of GB being more pronounced than those of HA. NS led to a considerable decrease in leaf total N and endogenous GB contents, stomatal conductance (g s), net photosynthetic rate (P n), intercellular CO2 concentration (C i), and activities of two key C4 photosynthesis enzymes phosphoenolpyruvate carboxylase (PEPCase) and ribulose-1,5-bisphosphate carboxylase (RuBPCase) as well as of superoxide dismutase (SOD) and peroxidase (POD). This treatment caused an increase in lipid peroxidation, but showed no effect on POD activity. Exogenous application of varying doses of GB resulted in a decrease in lipid peroxidation and C i, and an increase in leaf total N and endogenous glycinebetaine (EGB) content, P n, and activities of RuBPCase, PEPCase, SOD, and catalase (CAT) under NS. In contrast, application of different doses of HA resulted in a decrease in lipid peroxidation, an increase in P n, g s, and C i as well as SOD, CAT, and POD activities without increasing leaf total N and EGB content, and enhanced RuBPCase and PEPCase activities. The present study suggests that exogenous application of GB and HA can induce tolerance in maize plants to NS, but through the regulation of different mechanisms.
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Claims 17
Claim · model-written summary
Nitrogen stress significantly reduced maize seedling dry matter.
Not reportedComparator
Verbatim
e0“NS caused a significant reduction in total dry matter of seedlings of ZD958”
Claim · model-written summary
Both glycinebetaine and humic acid mitigated nitrogen-stress inhibition of seedling dry matter, with glycinebetaine more effective.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“both GB and HA proved effective in mitigating this inhibition, hence, the beneficial effects of GB being more pronounced than those of HA”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
Claim · model-written summary
Nitrogen stress decreased leaf nitrogen and endogenous glycinebetaine content.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NS led to a considerable decrease in leaf total N and endogenous GB contents”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
Claim · model-written summary
Nitrogen stress decreased stomatal conductance, net photosynthetic rate and intercellular CO2 concentration.
- Treatment
- NSe0
- Outcome
- stomatal conductance (g s), net photosynthetic rate (P n), intercellular CO2 concentration (C i)e0
- Direction
- decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NS led to a considerable decrease in leaf total N and endogenous GB contents, stomatal conductance (g s), net photosynthetic rate (P n), intercellular CO2 concentration (C i)”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
Claim · model-written summary
Nitrogen stress decreased PEPCase and RuBPCase activities.
- Treatment
- NSe0
- Outcome
- activities of two key C4 photosynthesis enzymes phosphoenolpyruvate carboxylase (PEPCase) and ribulose-1,5-bisphosphate carboxylase (RuBPCase)e0
- Direction
- decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NS led to a considerable decrease in leaf total N and endogenous GB contents, stomatal conductance (g s), net photosynthetic rate (P n), intercellular CO2 concentration (C i), and activities of two key C4 photosynthesis enzymes phosphoenolpyruvate carboxylase (PEPCase) and ribulose-1,5-bisphosphate carboxylase (RuBPCase)”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
Claim · model-written summary
Nitrogen stress decreased superoxide dismutase activity.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“as well as of superoxide dismutase (SOD) and peroxidase (POD)”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
Claim · model-written summary
Nitrogen stress increased lipid peroxidation.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This treatment caused an increase in lipid peroxidation”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
Claim · model-written summary
Nitrogen stress had no reported effect on POD activity.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but showed no effect on POD activity”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
Claim · model-written summary
Glycinebetaine lowered lipid peroxidation and intercellular CO2 under nitrogen stress.
- Treatment
- Exogenous application of varying doses of GBe0
- Outcome
- lipid peroxidation and C ie0
- Direction
- decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exogenous application of varying doses of GB resulted in a decrease in lipid peroxidation and C i”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
Claim · model-written summary
Glycinebetaine increased leaf total nitrogen, endogenous glycinebetaine and photosynthetic rate under nitrogen stress.
- Treatment
- GBe1
- Outcome
- leaf total N and endogenous glycinebetaine (EGB) content, P ne0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“an increase in leaf total N and endogenous glycinebetaine (EGB) content, P n”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
e1“Exogenous application of varying doses of GB”
Claim · model-written summary
Glycinebetaine increased RuBPCase, PEPCase and SOD activities under nitrogen stress.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“activities of RuBPCase, PEPCase, SOD, and catalase (CAT) under NS”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
e1“Exogenous application of varying doses of GB”
Claim · model-written summary
Glycinebetaine increased catalase activity under nitrogen stress.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“activities of RuBPCase, PEPCase, SOD, and catalase (CAT) under NS”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
e1“Exogenous application of varying doses of GB”
Claim · model-written summary
Humic acid decreased lipid peroxidation under nitrogen stress.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“application of different doses of HA resulted in a decrease in lipid peroxidation”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
Claim · model-written summary
Humic acid increased photosynthetic rate, stomatal conductance and intercellular CO2 under nitrogen stress.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“an increase in P n, g s, and C i”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
e1“application of different doses of HA”
Claim · model-written summary
Humic acid increased SOD, CAT and POD activities under nitrogen stress.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SOD, CAT, and POD activities without increasing leaf total N and EGB content”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
e1“application of different doses of HA”
Claim · model-written summary
Humic acid did not increase leaf nitrogen or endogenous glycinebetaine content.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“without increasing leaf total N and EGB content”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
e1“application of different doses of HA”
Claim · model-written summary
Humic acid enhanced RuBPCase and PEPCase activities.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“enhanced RuBPCase and PEPCase activities”
t0“Exogenous glycinebetaine and humic acid improve growth, nitrogen status, photosynthesis, and antioxidant defense system and confer tolerance to nitrogen stress in maize seedlings”
t1“nitrogen stress in maize seedlings”
e1“application of different doses of HA”
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See all 39 papers →8 of 14 groups shown: named compounds and organisms first, then groups whose results differ (checked claim by claim), then those with positive and negative results, then the smaller groups.
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.