Abstract
In this study, the differences in chlorophyll fluorescence transient (OJIP) and modulated 820 nm reflection (MR 820 ) of cucumber leaves were probed to demonstrate an insight into the precise influence of melatonin (MT) on cucumber photosystems under low temperature stress. We pre-treated cucumber seedlings with different levels of MT (0, 25, 50, 100, 200, and 400 μmol · L -1 ) before imposing low temperature stress (10 °C/6 °C). The results indicated that moderate concentrations of MT had a positive effect on the growth of low temperature-stressed cucumber seedlings. Under low temperature stress conditions, 100 μmol · L -1 (MT 100) improved the performance of the active photosystem II (PSII) reaction centers (PIabs), the oxygen evolving complex activity (OEC centers) and electron transport between PSII and PSI, mainly by decreasing the L-band, K-band, and G-band, but showed differences with different duration of low temperature stress. In addition, these indicators related to quantum yield and energy flux of PSII regulated by MT indicated that MT (MT 100) effectively protected the electron transport and energy distribution in the photosystem. According to the results of W O-I ≥ 1 and MR 820 signals, MT also affected PSI activity. MT 100 decreased the minimal value of MR/MR O and the oxidation rate of plastocyanin (PC) and PSI reaction center (P700) ( V ox ), while increased △MR slow /MR O and deoxidation rates of PC + and P 700 + ( V red ). The loss of the slow phase of MT 200 and MT 400-treated plants in the MR 820 kinetics was due to the complete prevention of electron movement from PSII to re-reduce the PC + and P700 + . These results suggest that appropriate MT concentration (100 μmol · L -1 ) can improve the photosynthetic performance of PS II and electron transport from primary quinone electron acceptor (Q A ) to secondary quinone electron acceptor (Q B ), promote the balance of energy distribution, strengthen the connectivity of PSI and PSII, improve the electron flow of PSII via Q A to PC + and P 700 + from reaching PSI by regulating multiple sites of electron transport chain in photosynthesis, and increase the pool size and reduction rates of PSI in low temperature-stressed cucumber plants, All these modifications by MT 100 treatment promoted the photosynthetic electron transfer smoothly, and further restored the cucumber plant growth under low temperature stress. Therefore, we conclude that spraying MT at an appropriate concentration is beneficial for protecting the photosynthetic electron transport chain, while spraying high concentrations of MT has a negative effect on regulating the low temperature tolerance in cucumber.
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Claims 14
Claim · model-written summary
Moderate concentrations of melatonin had a positive effect on the growth of low-temperature-stressed cucumber seedlings.
- Taxon
- cucumber
Cucumis sativuse0 - Treatment
- moderate concentrations of MTe0
- Outcome
- growthe0
- Direction
- positive effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e0“The results indicated that moderate concentrations of MT had a positive effect on the growth of low temperature-stressed cucumber seedlings”
Claim · model-written summary
Melatonin at 100 μmol · L -1 improved the performance of PSII reaction centres, the oxygen evolving complex activity and electron transport between PSII and PSI under low-temperature stress, with the effect differing by stress duration.
- Taxon
- cucumberCucumis sativust0
- Treatment
- 100 μmol · L -1 (MT 100)e1
- Outcome
- the performance of the active photosystem II (PSII) reaction centers (PIabs), the oxygen evolving complex activity (OEC centers) and electron transport between PSII and PSIe1
- Direction
- improvede1
- Qualifier
- showed differences with different duration of low temperature stresse1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e1“Under low temperature stress conditions, 100 μmol · L -1 (MT 100) improved the performance of the active photosystem II (PSII) reaction centers (PIabs), the oxygen evolving complex activity (OEC centers) and electron transport between PSII and PSI, mainly by decreasing the L-band, K-band, and G-band, but showed differences with different duration of low temperature stress”
Claim · model-written summary
Melatonin at 100 μmol · L -1 decreased the L-band, K-band and G-band of the chlorophyll fluorescence transient under low-temperature stress.
- Taxon
- cucumberCucumis sativust0
- Treatment
- 100 μmol · L -1 (MT 100)e1
- Outcome
- L-band, K-band, and G-bande1
- Direction
- decreasinge1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e1“Under low temperature stress conditions, 100 μmol · L -1 (MT 100) improved the performance of the active photosystem II (PSII) reaction centers (PIabs), the oxygen evolving complex activity (OEC centers) and electron transport between PSII and PSI, mainly by decreasing the L-band, K-band, and G-band, but showed differences with different duration of low temperature stress”
Claim · model-written summary
Melatonin at 100 μmol · L -1 effectively protected electron transport and energy distribution in the photosystem.
- Taxon
- cucumberCucumis sativust0
- Treatment
- MT (MT 100)e7
- Outcome
- electron transport and energy distribution in the photosysteme7
- Direction
- effectively protectede7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e7“MT (MT 100) effectively protected the electron transport and energy distribution in the photosystem”
Claim · model-written summary
Melatonin at 100 μmol · L -1 decreased the minimal value of MR/MRo and the oxidation rate of plastocyanin and P700 (Vox) in cucumber under low-temperature stress.
- Taxon
- cucumberCucumis sativust0
- Treatment
- MT 100e2
- Outcome
- minimal value of MR/MR O and the oxidation rate of plastocyanin (PC) and PSI reaction center (P700) ( V ox )e2
- Direction
- decreasede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e2“MT 100 decreased the minimal value of MR/MR O and the oxidation rate of plastocyanin (PC) and PSI reaction center (P700) ( V ox )”
Claim · model-written summary
Melatonin at 100 μmol · L -1 increased the deoxidation rates of PC+ and P700+ (Vred) and the slow-phase MR ratio in cucumber under low-temperature stress.
- Taxon
- cucumberCucumis sativust0
- Treatment
- MT 100e2
- Outcome
- △MR slow /MR O and deoxidation rates of PC + and P 700 + ( V red )e3
- Direction
- increasede3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e2“MT 100 decreased the minimal value of MR/MR O and the oxidation rate of plastocyanin (PC) and PSI reaction center (P700) ( V ox )”
e3“increased △MR slow /MR O and deoxidation rates of PC + and P 700 + ( V red )”
Claim · model-written summary
Melatonin at 200 and 400 μmol · L -1 lost the slow phase of the MR820 kinetics, which the authors attribute to complete prevention of electron movement from PSII to re-reduce PC+ and P700+.
- Taxon
- cucumberCucumis sativust0
- Treatment
- MT 200 and MT 400e4
- Outcome
- loss of the slow phasee4
- Qualifier
- complete prevention of electron movement from PSII to re-reduce the PC + and P700 +e4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e4“The loss of the slow phase of MT 200 and MT 400-treated plants in the MR 820 kinetics was due to the complete prevention of electron movement from PSII to re-reduce the PC + and P700 +”
Claim · model-written summary
An appropriate melatonin concentration of 100 μmol · L -1 is suggested to improve electron transport from QA to QB in cucumber under low-temperature stress.
- Taxon
- cucumberCucumis sativust0
- Treatment
- appropriate MT concentration (100 μmol · L -1 )e6
- Outcome
- electron transport from primary quinone electron acceptor (Q A ) to secondary quinone electron acceptor (Q B )e6
- Direction
- improvee6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e6“appropriate MT concentration (100 μmol · L -1 ) can improve the photosynthetic performance of PS II and electron transport from primary quinone electron acceptor (Q A ) to secondary quinone electron acceptor (Q B )”
Claim · model-written summary
An appropriate melatonin concentration increased the pool size and reduction rates of PSI in low-temperature-stressed cucumber.
- Taxon
- cucumberCucumis sativust0
- Treatment
- appropriate MT concentratione6
- Outcome
- pool size and reduction rates of PSIe7
- Direction
- increasee7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e6“appropriate MT concentration (100 μmol · L -1 ) can improve the photosynthetic performance of PS II and electron transport from primary quinone electron acceptor (Q A ) to secondary quinone electron acceptor (Q B )”
e7“increase the pool size and reduction rates of PSI in low temperature-stressed cucumber plants”
Claim · model-written summary
An appropriate melatonin concentration strengthened the connectivity of PSI and PSII in cucumber under low-temperature stress.
- Taxon
- cucumberCucumis sativust0
- Treatment
- appropriate MT concentratione6
- Outcome
- connectivity of PSI and PSIIe7
- Direction
- strengthene7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e6“appropriate MT concentration (100 μmol · L -1 ) can improve the photosynthetic performance of PS II and electron transport from primary quinone electron acceptor (Q A ) to secondary quinone electron acceptor (Q B )”
e7“promote the balance of energy distribution, strengthen the connectivity of PSI and PSII”
Claim · model-written summary
An appropriate melatonin concentration promoted the balance of energy distribution in cucumber under low-temperature stress.
- Taxon
- cucumberCucumis sativust0
- Treatment
- appropriate MT concentratione6
- Outcome
- balance of energy distributione7
- Direction
- promotee7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e6“appropriate MT concentration (100 μmol · L -1 ) can improve the photosynthetic performance of PS II and electron transport from primary quinone electron acceptor (Q A ) to secondary quinone electron acceptor (Q B )”
e7“promote the balance of energy distribution, strengthen the connectivity of PSI and PSII”
Claim · model-written summary
Melatonin at 100 μmol · L -1 further restored cucumber plant growth under low-temperature stress.
- Taxon
- cucumberCucumis sativuse5
- Treatment
- MT 100 treatmente5
- Outcome
- the cucumber plant growthe5
- Direction
- restorede5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e5“All these modifications by MT 100 treatment promoted the photosynthetic electron transfer smoothly, and further restored the cucumber plant growth under low temperature stress”
Claim · model-written summary
Spraying melatonin at an appropriate concentration is beneficial for protecting the photosynthetic electron transport chain of cucumber.
- Taxon
- cucumberCucumis sativust0
- Treatment
- spraying MT at an appropriate concentratione7
- Outcome
- protecting the photosynthetic electron transport chaine7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e7“we conclude that spraying MT at an appropriate concentration is beneficial for protecting the photosynthetic electron transport chain”
Claim · model-written summary
Spraying high concentrations of melatonin has a negative effect on low-temperature tolerance in cucumber.
- Taxon
- cucumberCucumis sativust0
- Treatment
- spraying high concentrations of MTe6
- Outcome
- regulating the low temperature tolerancee6
- Direction
- negative effecte6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“photosynthetic electron transport under low-temperature stress in cucumber”
e6“spraying high concentrations of MT has a negative effect on regulating the low temperature tolerance in cucumber”
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