Abstract
The effects of exogenous spermidine (Spd, 1 mmol·L-1) on photosynthetic characteristics, xanthophylls cycle components and endogenous polyamines levels were investigated in cucumber seedlings subjected to salt stress (75 mmol·L-1 NaCl). Chlorophyll contents and net photosynthetic rate (PN) of cucumber seedlings showed a significant decrease under salinity but an increase with exogenous Spd application. Salt stress caused a remarkable decline in the maximum quantum efficiency (Fv/Fm) and the actual efficiency of photosystem II (ФPSⅡ), where an increase was observed in the constitutive loss processes (ΦNO). Application of exogenous Spd significantly decreased ФNO and enhanced regulated non-photochemical energy loss (ФNPQ) in the salt-stressed plants. Spd treatment caused an increase in the size of xanthophyll cycle pool (VAZ) and further enhanced de-epoxidation of the xanthophyll cycle (DEPS) under salt stress. These results suggest that exogenous Spd alleviated salt-mediated decline in photosynthetic efficiency through the enhanced involvement of the energy dissipation that is dependent on the xanthophyll cycle. In addition, foliar spray Spd significantly increased the free, bound and conjugated polyamines in the leaves of the salt stressed plants. Spd also increased the free putrescine (Put)/(Spd+Spm) ratio and decreased bound and conjugated Put/(Spd+Spm) under salinity. Thus, we conclude that Spd can alleviate salt-induced damage on cucumber seedlings by regulating the levels of endogenous polyamines, which was associated with an improvement in the photochemical efficiency of PSII of the salt stressed plants. Key words: Cucumber, endogenous polyamines, photosynthetic characteristics, salt stress, spermidine.
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Claims 11
Claim · model-written summary
Salinity significantly decreased chlorophyll content and net photosynthetic rate.
- Taxon
- cucumber seedlings
Cucumis sativuse0 - Treatment
- salinitye0
- Outcome
- Chlorophyll contents and net photosynthetic rate (PN)e0
- Direction
- decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Chlorophyll contents and net photosynthetic rate (PN) of cucumber seedlings showed a significant decrease under salinity”
Claim · model-written summary
Exogenous Spd increased chlorophyll content and net photosynthetic rate.
- Taxon
- cucumber seedlingsCucumis sativuse0
- Treatment
- exogenous Spd applicatione0
- Outcome
- Chlorophyll contents and net photosynthetic rate (PN)e0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Chlorophyll contents and net photosynthetic rate (PN) of cucumber seedlings showed a significant decrease under salinity but an increase with exogenous Spd application.”
Claim · model-written summary
Salt stress reduced Fv/Fm and ФPSⅡ.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- Salt stresse0
- Outcome
- maximum quantum efficiency (Fv/Fm) and the actual efficiency of photosystem II (ФPSⅡ)e0
- Direction
- declinee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Salt stress caused a remarkable decline in the maximum quantum efficiency (Fv/Fm) and the actual efficiency of photosystem II (ФPSⅡ)”
t0“cucumber seedlings”
Claim · model-written summary
Salt stress increased ΦNO.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- Salt stresse0
- Outcome
- constitutive loss processes (ΦNO)e0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Salt stress caused a remarkable decline in the maximum quantum efficiency (Fv/Fm) and the actual efficiency of photosystem II (ФPSⅡ), where an increase was observed in the constitutive loss processes (ΦNO).”
t0“cucumber seedlings”
Claim · model-written summary
Spd significantly decreased ФNO under salt stress.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- exogenous Spde0
- Outcome
- ФNOe0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Application of exogenous Spd significantly decreased ФNO and enhanced regulated non-photochemical energy loss (ФNPQ) in the salt-stressed plants.”
t0“cucumber seedlings”
Claim · model-written summary
Spd enhanced ФNPQ under salt stress.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- exogenous Spde0
- Outcome
- regulated non-photochemical energy loss (ФNPQ)e0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Application of exogenous Spd significantly decreased ФNO and enhanced regulated non-photochemical energy loss (ФNPQ) in the salt-stressed plants.”
t0“cucumber seedlings”
Claim · model-written summary
Spd increased VAZ and DEPS under salt stress.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- Spd treatmente0
- Outcome
- size of xanthophyll cycle pool (VAZ)e0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Spd treatment caused an increase in the size of xanthophyll cycle pool (VAZ) and further enhanced de-epoxidation of the xanthophyll cycle (DEPS) under salt stress.”
t0“cucumber seedlings”
Claim · model-written summary
Spd enhanced DEPS under salt stress.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- Spd treatmente0
- Outcome
- de-epoxidation of the xanthophyll cycle (DEPS)e0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Spd treatment caused an increase in the size of xanthophyll cycle pool (VAZ) and further enhanced de-epoxidation of the xanthophyll cycle (DEPS) under salt stress.”
t0“cucumber seedlings”
Claim · model-written summary
Spd significantly increased free, bound and conjugated leaf polyamines under salt stress.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- foliar spray Spde0
- Outcome
- free, bound and conjugated polyamines in the leavese0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“foliar spray Spd significantly increased the free, bound and conjugated polyamines in the leaves of the salt stressed plants.”
t0“cucumber seedlings”
Claim · model-written summary
Spd increased the free Put/(Spd+Spm) ratio under salinity.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- Spde0
- Outcome
- free putrescine (Put)/(Spd+Spm) ratioe0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Spd also increased the free putrescine (Put)/(Spd+Spm) ratio and decreased bound and conjugated Put/(Spd+Spm) under salinity.”
t0“cucumber seedlings”
Claim · model-written summary
Spd decreased bound and conjugated Put/(Spd+Spm) under salinity.
- Taxon
- cucumber seedlingsCucumis sativust0
- Treatment
- Spde0
- Outcome
- bound and conjugated Put/(Spd+Spm)e0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Spd also increased the free putrescine (Put)/(Spd+Spm) ratio and decreased bound and conjugated Put/(Spd+Spm) under salinity.”
t0“cucumber seedlings”
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