Abstract
Plants evolved photoprotective mechanisms in order to counteract the damaging effects of excess light in oxygenic environments. Among them, chloroplast avoidance and non-photochemical quenching concur in reducing the concentration of chlorophyll excited states in the photosynthetic apparatus to avoid photooxidation. We evaluated their relative importance in regulating excitation pressure on photosystem II. To this aim, genotypes were constructed carrying mutations impairing the chloroplast avoidance response (phot2) as well as mutations affecting the biosynthesis of the photoprotective xanthophyll zeaxanthin (npq1) or the activation of non-photochemical quenching (npq4), followed by evaluation of their photosensitivity in vivo. Suppression of avoidance response resulted in oxidative stress under excess light at low temperature, while removing either zeaxanthin or PsbS had a milder effect. The double mutants phot2 npq1 and phot2 npq4 showed the highest sensitivity to photooxidative stress, indicating that xanthophyll cycle and qE have additive effects over the avoidance response. The interactions between non-photochemical quenching and avoidance responses were studied by analyzing the kinetics of fluorescence decay and recovery at different light intensities. phot2 fluorescence decay lacked a component, here named as qM. This kinetic component linearly correlated with the leaf transmittance changes due to chloroplast relocation induced by white light and was absent when red light was used as actinic source. On these basis we conclude that a decrease in leaf optical density affects the apparent non-photochemical quenching (NPQ) rise kinetic. Thus, excess light-induced fluorescence decrease is in part due to avoidance of photon absorption rather than to a genuine quenching process.
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Claims 8
Claim · model-written summary
Suppressing the chloroplast avoidance response caused oxidative stress under excess light at low temperature.
- Taxon
- Arabidopsis
Arabidopsist0 - Treatment
- Suppression of avoidance responsee1
- Outcome
- oxidative stresse1
- Qualifier
- under excess light at low temperaturee1
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Suppression of avoidance response resulted in oxidative stress under excess light at low temperature, while removing either zeaxanthin or PsbS had a milder effect”
t0“Arabidopsis”
Claim · model-written summary
Removing zeaxanthin or PsbS had a milder effect on oxidative stress than suppressing the avoidance response.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- removing either zeaxanthin or PsbSe1
- Outcome
- oxidative stresse1
- Direction
- mildere1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Suppression of avoidance response resulted in oxidative stress under excess light at low temperature, while removing either zeaxanthin or PsbS had a milder effect”
t0“Arabidopsis”
Claim · model-written summary
The phot2 npq1 and phot2 npq4 double mutants showed the highest sensitivity to photooxidative stress.
- Taxon
- ArabidopsisArabidopsist0
- Material
- phot2 npq1 and phot2 npq4e3
- Outcome
- sensitivity to photooxidative stresse3
- Direction
- higheste3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“The double mutants phot2 npq1 and phot2 npq4 showed the highest sensitivity to photooxidative stress”
t0“Arabidopsis”
Claim · model-written summary
The xanthophyll cycle and qE have additive effects over the chloroplast avoidance response against photooxidative stress.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- sensitivity to photooxidative stresse4
- Qualifier
- xanthophyll cycle and qE have additive effects over the avoidance responsee4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“showed the highest sensitivity to photooxidative stress, indicating that xanthophyll cycle and qE have additive effects over the avoidance response”
t0“Arabidopsis”
Claim · model-written summary
The phot2 mutant fluorescence decay lacks a component, named qM.
- Taxon
- ArabidopsisArabidopsist0
- Material
- phot2e5
- Outcome
- fluorescence decaye5
- Qualifier
- lacked a component, here named as qMe5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e5“phot2 fluorescence decay lacked a component, here named as qM”
t0“Arabidopsis”
Claim · model-written summary
The qM component correlates linearly with leaf transmittance changes from chloroplast relocation under white light and is absent under red light.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- white lighte6
- Outcome
- kinetic componente6
- Comparator
- red lighte6
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e6“This kinetic component linearly correlated with the leaf transmittance changes due to chloroplast relocation induced by white light and was absent when red light was used as actinic source”
t0“Arabidopsis”
Claim · model-written summary
A decrease in leaf optical density affects the apparent NPQ rise kinetic.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- apparent non-photochemical quenching (NPQ) rise kinetice7
- Qualifier
- a decrease in leaf optical densitye7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“we conclude that a decrease in leaf optical density affects the apparent non-photochemical quenching (NPQ) rise kinetic”
t0“Arabidopsis”
Claim · model-written summary
Excess light-induced fluorescence decrease is partly due to avoidance of photon absorption rather than genuine quenching.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- excess light-induced fluorescence decreasee7
- Qualifier
- avoidance of photon absorptione7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“excess light-induced fluorescence decrease is in part due to avoidance of photon absorption rather than to a genuine quenching process”
t0“Arabidopsis”
The same questions in other papers
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loss of function · physiology: oxidative · ArabidopsisPositive and negative results
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- negative
- positive
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See all 22 papers →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.