Abstract
To understand the effect of ultraviolet (UV)-B irradiation on the antioxidant capacity and growth of lettuce (Lactuca sativa), we subjected lettuce plants to UV-B irradiation (15.55 kJ m−2 d−1) for 7 days and measured yield, photosynthetic performance, hydrogen peroxide (H2O2), reduced glutathione (GSH), and ascorbic acid (AsA) contents, and the enzyme activity and expression of genes involving AsA recycling. UV-B exposure did not significantly decrease the fresh/dry weight of the lettuce shoots. The net photosynthesis rate, internal CO2 concentration, transpiration rate, and stomatal conductance decreased during the first 4 days of irradiation and light but recovered at day 7. In UV-B-treated plants, the levels of AsA, GSH, and H2O2 increased significantly and simultaneously, with a positive correlation found between H2O2 and AsA or GSH levels. UV-B exposure upregulated the expression level of most genes encoding the enzymes involving AsA recycling but downregulated the associated enzymatic activities. The increase of AsA content in UV-B-exposed lettuce might contribute to the AsA–GSH cycle, leading to downregulation of ascorbate oxidase (AO) enzymatic activity and gene expression. UV-B irradiation had a greater impact on metabolite levels than time of UV-B treatment. These results suggest that AsA homeostasis in UV-B-treated lettuce is regulated through a feedback loop between the expression and activity of enzymes associated with AsA recycling. Short-term UV-B supplementation (24 h) could be a promising approach to enhance AsA content in lettuce.
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Claims 10
Claim · model-written summary
UV-B did not significantly decrease lettuce shoot fresh or dry weight.
- Taxon
- lettuce
Lactuca sativae0 - Organ / stage
- shootse0
- Treatment
- UV-B exposuree0
- Outcome
- fresh/dry weight of the lettuce shootse0
- Direction
- did not significantly decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“UV-B exposure did not significantly decrease the fresh/dry weight of the lettuce shoots”
Claim · model-written summary
Photosynthetic gas exchange measures fell during the first four irradiation days and recovered at day seven.
- Treatment
- UV-B irradiation (15.55 kJ m−2 d−1)e1
- Outcome
- net photosynthesis rate, internal CO2 concentration, transpiration rate, and stomatal conductancee0
- Direction
- decreasede0
- Qualifier
- recovered at day 7e0
Not reportedTaxonComparator
Verbatim
e0“The net photosynthesis rate, internal CO2 concentration, transpiration rate, and stomatal conductance decreased during the first 4 days of irradiation and light but recovered at day 7”
e1“UV-B irradiation (15.55 kJ m−2 d−1) for 7 days”
Claim · model-written summary
UV-B increased lettuce AsA, GSH and H2O2 levels significantly.
- Taxon
- lettuceLactuca sativae1
- Treatment
- UV-B-treatede0
- Outcome
- levels of AsA, GSH, and H2O2e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In UV-B-treated plants, the levels of AsA, GSH, and H2O2 increased significantly and simultaneously”
e1“lettuce (Lactuca sativa)”
Claim · model-written summary
H2O2 level correlated positively with AsA and GSH levels.
- Taxon
- lettuceLactuca sativae1
- Compound
- H2O2e0
- Outcome
- AsA or GSH levelse0
- Direction
- positivee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a positive correlation found between H2O2 and AsA or GSH levels”
e1“lettuce (Lactuca sativa)”
Claim · model-written summary
UV-B upregulated expression of most genes encoding AsA recycling enzymes.
- Taxon
- lettuceLactuca sativae1
- Treatment
- UV-B exposuree0
- Outcome
- expression level of most genes encoding the enzymes involving AsA recyclinge0
- Direction
- upregulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“UV-B exposure upregulated the expression level of most genes encoding the enzymes involving AsA recycling”
e1“lettuce (Lactuca sativa)”
Claim · model-written summary
UV-B downregulated associated AsA recycling enzyme activities.
- Taxon
- lettuceLactuca sativae2
- Treatment
- UV-B exposuree1
- Outcome
- associated enzymatic activitiese0
- Direction
- downregulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but downregulated the associated enzymatic activities”
e1“UV-B exposure upregulated the expression level of most genes encoding the enzymes involving AsA recycling”
e2“lettuce (Lactuca sativa)”
Claim · model-written summary
The authors propose that elevated AsA contributes to the AsA–GSH cycle and downregulates AO activity and expression.
- Taxon
- lettuceLactuca sativae0
- Gene
- ascorbate oxidase (AO)e0
- Compound
- AsAe0
- Outcome
- downregulation of ascorbate oxidase (AO) enzymatic activity and gene expressione0
- Qualifier
- might contribute to the AsA–GSH cyclee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The increase of AsA content in UV-B-exposed lettuce might contribute to the AsA–GSH cycle, leading to downregulation of ascorbate oxidase (AO) enzymatic activity and gene expression”
Claim · model-written summary
UV-B irradiation affected metabolite levels more than treatment time.
- Taxon
- lettuceLactuca sativae1
- Outcome
- metabolite levelse0
- Direction
- greater impacte0
- Comparator
- time of UV-B treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“UV-B irradiation had a greater impact on metabolite levels than time of UV-B treatment”
e1“lettuce (Lactuca sativa)”
Claim · model-written summary
The authors suggest feedback between AsA recycling enzyme expression and activity regulates AsA homeostasis.
- Taxon
- lettuceLactuca sativae0
- Outcome
- AsA homeostasise0
- Qualifier
- feedback loop between the expression and activity of enzymes associated with AsA recyclinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AsA homeostasis in UV-B-treated lettuce is regulated through a feedback loop between the expression and activity of enzymes associated with AsA recycling”
Claim · model-written summary
The authors recommend short-term UV-B supplementation to enhance lettuce AsA content.
- Taxon
- lettuceLactuca sativae0
- Treatment
- Short-term UV-B supplementation (24 h)e0
- Outcome
- enhance AsA contente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Short-term UV-B supplementation (24 h) could be a promising approach to enhance AsA content in lettuce”
The same questions in other papers
uv · growth · Lactuca sativa (garden lettuce)Results differ
19 papers in the same direction as this paper · 15 in the opposite direction
- positive
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1 paper in the same direction as this paper · 1 in the opposite direction
- negative
- positive
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.