Abstract
Lead (Pb) is a heavy metal pollutant and negatively affects agriculture and ecosystems. Pb can cause oxidative stress and abnormal plant growth. The ascorbic acid-glutathione (AsA-GSH) cycle mainly exists in chloroplasts and resists oxidative stress, scavenges reactive oxygen radicals, and maintains normal photosynthesis. However, the dosage related effects of Pb on pakchoi photosynthesis, via oxidative stress and the AsA-GSH system, remains unclear. In this study, various Pb dosage stress models were tested (low: 300 mg/kg; medium: 600 mg/kg; high: 900 mg/kg). Pb stress induced a dose-dependent increase in Pb content in pakchoi leaves (P < 0.05). Principal component analysis showed that Se, B, and Pb were significantly and negatively correlated. Pb stress also increased MDA content and decreased antioxidant enzymes SOD, GSH-Px, and T-AOC activities (P < 0.05). We also found that Vc content, as well as the GSH/GSSG ratio, decreased. Additionally, Pb stress destroyed chloroplast structure, decreased photosynthesis indicators Pn, Tr, Gs, Ci and VPD, and attenuated Fv/Fm and Fv/Fo (P < 0.05). In the high-dose group, the contents of chlorophyll a, chlorophyll b, and carotenoids decreased significantly, while the expression of chloroplast development genes (GLK, GLN2) decreased (P < 0.05). Our data suggest that Pb stress leads to dosage-dependent, aberrant photosynthesis by inhibiting the AsA-GSH system in pakchoi. This study expands the Pb toxicology research field and provides indications for screening antagonists.
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Claims 11
Claim · model-written summary
Lead stress increased lead content in pakchoi leaves in a dose-dependent manner.
- Taxon
- pakchoie1
- Organ / stage
- leavese1
- Treatment
- Pb stresse1
- Outcome
- Pb contente1
- Direction
- increasee1
- Qualifier
- dose-dependente1
Not reportedComparator
Verbatim
e1“Pb stress induced a dose-dependent increase in Pb content in pakchoi leaves (P < 0.05)”
t0“in pakchoi (Brassica chinensis L.)”
Claim · model-written summary
Lead stress increased malondialdehyde (MDA) content in pakchoi.
Not reportedComparator
Verbatim
e2“Pb stress also increased MDA content and decreased antioxidant enzymes SOD, GSH-Px, and T-AOC activities (P < 0.05)”
t0“in pakchoi (Brassica chinensis L.)”
Claim · model-written summary
Lead stress decreased the activities of antioxidant enzymes SOD, GSH-Px and T-AOC in pakchoi.
- Taxon
- pakchoit0
- Treatment
- Pb stresse2
- Outcome
- antioxidant enzymes SOD, GSH-Px, and T-AOC activitiese2
- Direction
- decreasede2
Not reportedComparator
Verbatim
e2“Pb stress also increased MDA content and decreased antioxidant enzymes SOD, GSH-Px, and T-AOC activities (P < 0.05)”
t0“in pakchoi (Brassica chinensis L.)”
Claim · model-written summary
Lead stress decreased Vc content and the GSH/GSSG ratio in pakchoi.
Not reportedComparator
Verbatim
e3“We also found that Vc content, as well as the GSH/GSSG ratio, decreased”
e2“Pb stress also increased MDA content and decreased antioxidant enzymes SOD, GSH-Px, and T-AOC activities (P < 0.05)”
t0“in pakchoi (Brassica chinensis L.)”
Claim · model-written summary
Lead stress destroyed chloroplast structure in pakchoi.
Verbatim
e4“Additionally, Pb stress destroyed chloroplast structure”
t0“in pakchoi (Brassica chinensis L.)”
Claim · model-written summary
Lead stress decreased photosynthesis indicators Pn, Tr, Gs, Ci and VPD in pakchoi.
- Taxon
- pakchoit0
- Treatment
- Pb stresse5
- Outcome
- photosynthesis indicatorse5
- Direction
- decreasede5
- Qualifier
- Pn, Tr, Gs, Ci and VPDe5
Not reportedComparator
Verbatim
e5“Additionally, Pb stress destroyed chloroplast structure, decreased photosynthesis indicators Pn, Tr, Gs, Ci and VPD, and attenuated Fv/Fm and Fv/Fo (P < 0.05)”
t0“in pakchoi (Brassica chinensis L.)”
Claim · model-written summary
Lead stress attenuated Fv/Fm and Fv/Fo in pakchoi.
Not reportedComparator
Verbatim
e5“Additionally, Pb stress destroyed chloroplast structure, decreased photosynthesis indicators Pn, Tr, Gs, Ci and VPD, and attenuated Fv/Fm and Fv/Fo (P < 0.05)”
t0“in pakchoi (Brassica chinensis L.)”
Claim · model-written summary
In the high-dose group, chlorophyll a, chlorophyll b and carotenoid contents decreased significantly in pakchoi.
- Taxon
- pakchoit0
- Treatment
- high-dose groupe6
- Outcome
- contents of chlorophyll a, chlorophyll b, and carotenoidse6
- Direction
- decreasede6
Not reportedComparator
Verbatim
e6“In the high-dose group, the contents of chlorophyll a, chlorophyll b, and carotenoids decreased significantly”
t0“in pakchoi (Brassica chinensis L.)”
Claim · model-written summary
In the high-dose group, expression of chloroplast development genes GLK and GLN2 decreased.
Verbatim
e6“In the high-dose group, the contents of chlorophyll a, chlorophyll b, and carotenoids decreased significantly”
e7“while the expression of chloroplast development genes (GLK, GLN2) decreased (P < 0.05)”
t0“in pakchoi (Brassica chinensis L.)”
Claim · model-written summary
Principal component analysis showed Se, B and Pb were significantly and negatively correlated in pakchoi.
Verbatim
e0“Principal component analysis showed that Se, B, and Pb were significantly and negatively correlated”
t0“in pakchoi (Brassica chinensis L.)”
Claim · model-written summary
Lead stress is suggested to impair photosynthesis in a dose-dependent way by inhibiting the AsA-GSH system in pakchoi.
Verbatim
e0“Our data suggest that Pb stress leads to dosage-dependent, aberrant photosynthesis by inhibiting the AsA-GSH system in pakchoi”
t0“in pakchoi (Brassica chinensis L.)”
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8 of 9 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.