Abstract
In this study, specific dynamic changes in growth, oxidative stress, ascorbate metabolism, and chlorophyll fluorescence were monitored during 12 days in lettuce plants exposed to continuous light (CL) of different intensities: low light (LL, 100 μmol·m-2·s-1), medium light (ML, 200 μmol·m-2·s-1), and high light (HL, 300 μmol·m-2·s-1). Lettuce plants grown under CL of higher light intensity gained greater biomass, dry weight ratio, root/shoot ratio, and specific leaf FW, but not leaf area. Both the reactive oxygen species (ROS) production and the lipid peroxidation degree, measured in terms of the malondialdehyde (MDA) levels, were progressively enhanced by increasing the light intensity of CL. Overall, the pool sizes of ascorbate (AsA) and glutathione, as well as the activities of enzymes involved in AsA metabolism, had positive correlations with light intensity under CL. Ascorbate peroxidase and dehydroascorbate reductase presented the maximal and minimal responses to light intensity, respectively, among all the studied enzymes. After 6 days under CL, ML and HL intensity caused reversible photoinhibition, represented by lower values of maximum quantum efficiency (Fv/Fm), effective quantum yield (ΦPSII), and photochemical quenching (qP) and a higher value of non-photochemical quenching (qN). However, this photoinhibition recovered on day 12 with increasing of Fv/Fm, ΦPSII, and qP. Taken together, under ML and HL conditions, greater AsA level could help maintain photosynthetic efficiency by elevating excess excitation energy dissipation, though ROS accumulation and lipid peroxidation could not be prevented in the long-term. Likewise, there was no dark period under LL condition, but no photooxidative stress was observed in lettuce. Thus, it is concluded that photooxidative stress induced by CL can be attributed to excessive daily light integral instead of circadian asynchrony.
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Claims 11
Claim · model-written summary
Higher continuous-light intensity increased lettuce biomass, dry weight ratio, root/shoot ratio and specific leaf fresh weight.
- Taxon
- Lettuce
Lactuca sativae0 - Treatment
- CL of higher light intensitye0
- Outcome
- biomass, dry weight ratio, root/shoot ratio, and specific leaf FWe0
- Direction
- greatere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lettuce plants grown under CL of higher light intensity gained greater biomass, dry weight ratio, root/shoot ratio, and specific leaf FW”
Claim · model-written summary
Higher continuous-light intensity did not increase lettuce leaf area.
- Taxon
- LettuceLactuca sativae0
- Treatment
- CL of higher light intensitye0
- Outcome
- leaf areae0
- Direction
- but note0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lettuce plants grown under CL of higher light intensity gained greater biomass, dry weight ratio, root/shoot ratio, and specific leaf FW, but not leaf area”
Claim · model-written summary
Increasing continuous-light intensity progressively enhanced reactive oxygen species production and lipid peroxidation in lettuce.
- Taxon
- LettuceLactuca sativat0
- Treatment
- increasing the light intensity of CLe0
- Outcome
- reactive oxygen species (ROS) production and the lipid peroxidation degreee0
- Direction
- progressively enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both the reactive oxygen species (ROS) production and the lipid peroxidation degree, measured in terms of the malondialdehyde (MDA) levels, were progressively enhanced by increasing the light intensity of CL”
t0“Lettuce”
Claim · model-written summary
Ascorbate and glutathione pools and ascorbate-metabolism enzyme activities correlated positively with continuous-light intensity in lettuce.
- Taxon
- LettuceLactuca sativat0
- Treatment
- light intensity under CLe0
- Outcome
- pool sizes of ascorbate (AsA) and glutathione, as well as the activities of enzymes involved in AsA metabolisme0
- Direction
- positive correlationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the pool sizes of ascorbate (AsA) and glutathione, as well as the activities of enzymes involved in AsA metabolism, had positive correlations with light intensity under CL”
t0“Lettuce”
Claim · model-written summary
Ascorbate peroxidase had the maximal response to continuous-light intensity among the enzymes studied in lettuce.
- Taxon
- LettuceLactuca sativat0
- Gene
- Ascorbate peroxidasee0
- Outcome
- maximale0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ascorbate peroxidase and dehydroascorbate reductase presented the maximal and minimal responses to light intensity, respectively, among all the studied enzymes”
t0“Lettuce”
Claim · model-written summary
Dehydroascorbate reductase had the minimal response to continuous-light intensity among the enzymes studied in lettuce.
- Taxon
- LettuceLactuca sativat0
- Gene
- dehydroascorbate reductasee0
- Outcome
- minimale0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ascorbate peroxidase and dehydroascorbate reductase presented the maximal and minimal responses to light intensity, respectively, among all the studied enzymes”
t0“Lettuce”
Claim · model-written summary
After six days, medium and high continuous-light intensities caused reversible photoinhibition in lettuce, with lower Fv/Fm, ΦPSII and qP and higher qN.
- Taxon
- LettuceLactuca sativat0
- Treatment
- ML and HL intensitye0
- Outcome
- reversible photoinhibitione0
- Direction
- lower valuese0
- Qualifier
- After 6 days under CLe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After 6 days under CL, ML and HL intensity caused reversible photoinhibition, represented by lower values of maximum quantum efficiency (Fv/Fm), effective quantum yield (ΦPSII), and photochemical quenching (qP) and a higher value of non-photochemical quenching (qN)”
t0“Lettuce”
Claim · model-written summary
By day 12, lettuce photoinhibition recovered as Fv/Fm, ΦPSII and qP increased.
- Taxon
- LettuceLactuca sativat0
- Outcome
- photoinhibitione0
- Direction
- recoverede0
- Qualifier
- on day 12e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this photoinhibition recovered on day 12 with increasing of Fv/Fm, ΦPSII, and qP”
t0“Lettuce”
Claim · model-written summary
Low continuous light caused no observed photooxidative stress in lettuce.
- Taxon
- lettuceLactuca sativae0
- Treatment
- LL conditione0
- Outcome
- photooxidative stresse0
- Direction
- no photooxidative stresse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was no dark period under LL condition, but no photooxidative stress was observed in lettuce”
Claim · model-written summary
The authors infer that greater ascorbate under medium and high continuous light could help maintain photosynthetic efficiency through excess excitation-energy dissipation in lettuce.
- Taxon
- LettuceLactuca sativat0
- Treatment
- ML and HL conditionse0
- Compound
- AsAe0
- Outcome
- photosynthetic efficiencye0
- Qualifier
- could helpe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under ML and HL conditions, greater AsA level could help maintain photosynthetic efficiency by elevating excess excitation energy dissipation”
t0“Lettuce”
Claim · model-written summary
The authors attribute photooxidative stress under continuous light to excessive daily light integral.
- Taxon
- LettuceLactuca sativat0
- Treatment
- CLe0
- Outcome
- photooxidative stresse0
- Qualifier
- excessive daily light integral instead of circadian asynchronye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photooxidative stress induced by CL can be attributed to excessive daily light integral instead of circadian asynchrony”
t0“Lettuce”
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