Abstract
Aims: The aim of the present study was to investigate some biochemical changes in field grown lettuce (Lactuca sativa L. cv Romaine) plants in terms of importance of the accumulation of anthocyanins, flavonoids and photosynthetic pigments as well as photosynthetic limitations which changed during exposure of plants to drought stress and UV-B radiation in order to circumvent the deleterious effects of these Stresses. Place and Duration of Study: The experiment was conducted under filed conditions from November 2012 to January 2013, at the Agricultural Research Center, KAU. Methodology: The experimental design was a factorial arrangement in randomized complete blocks with four replicates. The first factor was UV-B (300 nm). The second factor was irrigation regime (complete irrigation to field capacity and limited irrigation. Gas exchange measurements were carried out using a LI-6200 portable IRGA. Chlorophyll fluorescence of Fv/Fm was measured by PAM 2000 fluorometer. Biochemical analyses and antioxidant enzymes assays were performed according to the appropriate methods. Results: Exposure of lettuce plants to enhanced UV-B radiation and drought stresses (DS) negatively and significantly affected the process of photosynthesis including CO2 assimilation (PN), stomatal conductance to water vapour (gs) and transpiration rate (E). However, the amplitude of the effects of both stressors was dependent on the interactions. This resulted in alleviation of the negative effect of drought on photosynthesis and transpiration by UV-B radiation as the water stress intensified. Intercellular CO2 (Ci) concentration was only reduced due to water stress compared to control plants. The maximum efficiency of photosystem II (Fv/Fm) was not affected by UV-B radiation stress but reduced by drought. There was an increase in the activities of some antioxidant due to both stresses when applied singly and in combination UV-B irradiation increased the contents of the UV-B absorbing compounds (carotenoids, soluble phenols, anthocyanins), while drought stress caused a notable increase in free proline content. Increase in content of Proline may be the drought-induced factor which plays a protective role in response to UV-B. Conclusion: UV-B radiation provoked in general more severe damage, evaluated as changes in the amounts of stress markers, than DS, when applied separately. Under multiple stress conditions, each of the stress factors seems to bring out some adaptive effects to reduce the damage experienced by plants caused by the other one. DS can induce accumulation of UV-B absorbing compounds (flavonoids, carotenoids and soluble phenols), which is likely to offer some increased protection from UV-B.
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Claims 12
Claim · model-written summary
UV-B and drought significantly reduced CO2 assimilation, conductance and transpiration.
- Taxon
- lettuce plants
Lactuca sativae0 - Treatment
- enhanced UV-B radiation and drought stresses (DS)e0
- Outcome
- CO2 assimilation (PN), stomatal conductance to water vapour (gs) and transpiration rate (E)e0
- Direction
- negativelye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exposure of lettuce plants to enhanced UV-B radiation and drought stresses (DS) negatively and significantly affected the process of photosynthesis including CO2 assimilation (PN), stomatal conductance to water vapour (gs) and transpiration rate (E).”
Claim · model-written summary
The two stresses interacted in their effect amplitude.
- Taxon
- lettuce plantsLactuca sativat0
- Treatment
- both stressorse0
- Outcome
- amplitude of the effectse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the amplitude of the effects of both stressors was dependent on the interactions.”
t0“lettuce plants”
Claim · model-written summary
UV-B alleviated drought effects on photosynthesis and transpiration as water stress intensified.
- Taxon
- lettuce plantsLactuca sativat0
- Treatment
- UV-B radiatione0
- Outcome
- photosynthesis and transpiratione0
- Direction
- alleviatione0
- Comparator
- droughte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This resulted in alleviation of the negative effect of drought on photosynthesis and transpiration by UV-B radiation as the water stress intensified.”
t0“lettuce plants”
Claim · model-written summary
Water stress alone reduced intercellular CO2 compared with controls.
- Taxon
- lettuce plantsLactuca sativat0
- Treatment
- water stresse0
- Outcome
- Intercellular CO2 (Ci) concentratione0
- Direction
- reducede0
- Comparator
- control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Intercellular CO2 (Ci) concentration was only reduced due to water stress compared to control plants.”
t0“lettuce plants”
Claim · model-written summary
UV-B did not affect maximum photosystem II efficiency.
- Taxon
- lettuce plantsLactuca sativat0
- Treatment
- UV-B radiation stresse0
- Outcome
- maximum efficiency of photosystem II (Fv/Fm)e0
- Direction
- not affectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The maximum efficiency of photosystem II (Fv/Fm) was not affected by UV-B radiation stress but reduced by drought.”
t0“lettuce plants”
Claim · model-written summary
Drought reduced maximum photosystem II efficiency.
- Taxon
- lettuce plantsLactuca sativat0
- Treatment
- droughte0
- Outcome
- maximum efficiency of photosystem II (Fv/Fm)e0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The maximum efficiency of photosystem II (Fv/Fm) was not affected by UV-B radiation stress but reduced by drought.”
t0“lettuce plants”
Claim · model-written summary
Each stress alone and both together increased some antioxidant activities.
- Taxon
- lettuce plantsLactuca sativat0
- Treatment
- both stresses when applied singly and in combinatione0
- Outcome
- activities of some antioxidante0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There was an increase in the activities of some antioxidant due to both stresses when applied singly and in combination”
t0“lettuce plants”
Claim · model-written summary
UV-B increased carotenoids, soluble phenols and anthocyanins.
- Taxon
- lettuce plantsLactuca sativat0
- Treatment
- UV-B irradiatione0
- Outcome
- contents of the UV-B absorbing compounds (carotenoids, soluble phenols, anthocyanins)e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“UV-B irradiation increased the contents of the UV-B absorbing compounds (carotenoids, soluble phenols, anthocyanins)”
t0“lettuce plants”
Claim · model-written summary
Drought increased free proline.
- Taxon
- lettuce plantsLactuca sativat0
- Treatment
- drought stresse0
- Outcome
- free proline contente0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“drought stress caused a notable increase in free proline content.”
t0“lettuce plants”
Claim · model-written summary
Proline may protect lettuce against UV-B under drought.
- Taxon
- lettuce plantsLactuca sativat0
- Compound
- Prolinee0
- Outcome
- protective role in response to UV-Be0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increase in content of Proline may be the drought-induced factor which plays a protective role in response to UV-B.”
t0“lettuce plants”
Claim · model-written summary
UV-B separately caused more severe stress marker damage than drought.
- Taxon
- lettuce plantsLactuca sativat0
- Treatment
- UV-B radiatione0
- Outcome
- damagee0
- Direction
- more severee0
- Comparator
- DSe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“UV-B radiation provoked in general more severe damage, evaluated as changes in the amounts of stress markers, than DS, when applied separately.”
t0“lettuce plants”
Claim · model-written summary
Drought can induce UV-B absorbing compounds that may protect against UV-B.
- Taxon
- lettuce plantsLactuca sativat0
- Treatment
- DSe0
- Outcome
- increased protection from UV-Be0
- Qualifier
- accumulation of UV-B absorbing compounds (flavonoids, carotenoids and soluble phenols)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“DS can induce accumulation of UV-B absorbing compounds (flavonoids, carotenoids and soluble phenols), which is likely to offer some increased protection from UV-B.”
t0“lettuce plants”
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drought · physiology: photosynthesis · Lactuca sativa (garden lettuce)Results agree
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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.