Abstract
The effects of chilling (CT, day/night temperatures of 12/10 °C, an irradiance of 250 μmol m-2 s-1), chilling combined with a low irradiance (CL, 12/10 °C, 80 μmol m-2 s-1), and a high temperature (HT, 42/40 °C, 250 μmol m-2 s-1) on chlorophyll content, chlorophyll fluorescence, and gas exchange were studied in two watermelon cultivars, ZJ8424 and YS01, differing in their resistance. The chlorophyll content, net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) decreased substantially, whereas the intercellular CO2 concentration (ci) increased when the two watermelon cultivars were grown under these stresses. The photosynthetic parameters showed greater changes at chilling than at the high temperature, and the CL caused a more pronounced inhibition in PN compared with the CT. After 2 d exposure to the CT, YS01 had higher PN, gs, and E, but a lower ci compared with ZJ8424. The maximum efficiency of photosystem (PS) II photochemistry (Fv/Fm), effective quantum yield of PS II photochemistry (ΦPSII), photochemical quenching (qP), and electron transport rate (ETR) decreased under the CT and CL but showed only a slight drop under the HT. All these stresses significantly increased non-photochemical quenching (NPQ). The CT brought more damage to the photosynthetic apparatus of leaves compared with the CL. In addition, after returning to normal conditions (25/15 °C, 250 μmol m-2 s-1) for 3 d, the photosynthetic parameters recovered to pre-stress levels in HT treated seedlings but not in CT treated seedlings. In conclusion, the low irradiance could help to alleviate the extent of photoinhibition of PS II photochemistry caused by chilling and cv. ZJ8424 was more sensitive to the extreme temperatures than cv. YS01.
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Claims 16
Claim · model-written summary
Stress decreased chlorophyll content, net photosynthetic rate and stomatal conductance.
- Taxon
- watermelon
Citrullus lanatust0 - Treatment
- stressese1
- Outcome
- chlorophyll content, net photosynthetic rate (PN), stomatal conductance (gs)e0
- Direction
- decreased substantiallye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The chlorophyll content, net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) decreased substantially”
e1“under these stresses”
t0“watermelon”
Claim · model-written summary
Stress decreased transpiration rate.
- Taxon
- watermelonCitrullus lanatust0
- Treatment
- stressese1
- Outcome
- transpiration rate (E)e0
- Direction
- decreased substantiallye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transpiration rate (E) decreased substantially”
e1“under these stresses”
t0“watermelon”
Claim · model-written summary
Stress increased intercellular CO2 concentration.
- Taxon
- watermelonCitrullus lanatust0
- Treatment
- stressese0
- Outcome
- intercellular CO2 concentration (ci)e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the intercellular CO2 concentration (ci) increased when the two watermelon cultivars were grown under these stresses”
t0“watermelon”
Claim · model-written summary
Photosynthetic parameters changed more under chilling than high temperature.
- Taxon
- watermelonCitrullus lanatust0
- Treatment
- chillinge0
- Outcome
- photosynthetic parameterse0
- Direction
- greater changese0
- Comparator
- the high temperaturee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The photosynthetic parameters showed greater changes at chilling than at the high temperature”
t0“watermelon”
Claim · model-written summary
Chilling with low irradiance inhibited net photosynthesis more than chilling alone.
- Taxon
- watermelonCitrullus lanatust0
- Treatment
- CLe0
- Outcome
- PNe0
- Direction
- more pronounced inhibitione0
- Comparator
- CTe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the CL caused a more pronounced inhibition in PN compared with the CT”
t0“watermelon”
Claim · model-written summary
After 2 days of chilling, YS01 had higher net photosynthesis, conductance and transpiration than ZJ8424.
- Taxon
- watermelonCitrullus lanatust0
- Material
- YS01e0
- Outcome
- PN, gs, and Ee0
- Direction
- highere0
- Qualifier
- After 2 d exposure to the CTe0
- Comparator
- ZJ8424e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After 2 d exposure to the CT, YS01 had higher PN, gs, and E, but a lower ci compared with ZJ8424”
t0“watermelon”
Claim · model-written summary
After 2 days of chilling, YS01 had lower intercellular CO2 concentration than ZJ8424.
- Taxon
- watermelonCitrullus lanatust0
- Material
- YS01e0
- Outcome
- cie0
- Direction
- lowere0
- Qualifier
- After 2 d exposure to the CTe0
- Comparator
- ZJ8424e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After 2 d exposure to the CT, YS01 had higher PN, gs, and E, but a lower ci compared with ZJ8424”
t0“watermelon”
Claim · model-written summary
Chilling and chilling with low irradiance decreased Fv/Fm, ΦPSII and qP.
- Taxon
- watermelonCitrullus lanatust0
- Treatment
- CT and CLe0
- Outcome
- Fv/Fm), effective quantum yield of PS II photochemistry (ΦPSII), photochemical quenching (qPe0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The maximum efficiency of photosystem (PS) II photochemistry (Fv/Fm), effective quantum yield of PS II photochemistry (ΦPSII), photochemical quenching (qP), and electron transport rate (ETR) decreased under the CT and CL”
t0“watermelon”
Claim · model-written summary
Chilling and chilling with low irradiance decreased electron transport rate.
- Taxon
- watermelonCitrullus lanatust0
- Treatment
- CT and CLe0
- Outcome
- electron transport rate (ETR)e0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“electron transport rate (ETR) decreased under the CT and CL”
t0“watermelon”
Claim · model-written summary
High temperature produced only a slight drop in PSII fluorescence parameters and electron transport.
- Taxon
- watermelonCitrullus lanatust0
- Treatment
- HTe0
- Outcome
- Fv/Fme1
- Direction
- slight drope0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but showed only a slight drop under the HT”
e1“(Fv/Fm)”
t0“watermelon”
Claim · model-written summary
All stresses significantly increased non-photochemical quenching.
- Taxon
- watermelonCitrullus lanatust0
- Treatment
- stressese0
- Outcome
- non-photochemical quenching (NPQ)e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“All these stresses significantly increased non-photochemical quenching (NPQ)”
t0“watermelon”
Claim · model-written summary
Chilling damaged the leaf photosynthetic apparatus more than chilling with low irradiance.
- Taxon
- watermelonCitrullus lanatust0
- Treatment
- CTe0
- Outcome
- damage to the photosynthetic apparatus of leavese0
- Direction
- more damagee0
- Comparator
- CLe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The CT brought more damage to the photosynthetic apparatus of leaves compared with the CL”
t0“watermelon”
Claim · model-written summary
Photosynthetic parameters recovered to pre-stress levels after high-temperature seedlings returned to normal conditions.
- Taxon
- watermelonCitrullus lanatust0
- Treatment
- HTe0
- Outcome
- photosynthetic parameterse0
- Direction
- recovered to pre-stress levelse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic parameters recovered to pre-stress levels in HT treated seedlings”
t0“watermelon”
Claim · model-written summary
Photosynthetic parameters failed to recover after chilling-treated seedlings returned to normal conditions.
- Taxon
- watermelonCitrullus lanatust0
- Treatment
- CTe0
- Outcome
- photosynthetic parameterse1
- Direction
- no_changeinferrede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but not in CT treated seedlings”
e1“the photosynthetic parameters recovered to pre-stress levels in HT treated seedlings”
t0“watermelon”
Claim · model-written summary
Low irradiance could alleviate chilling-induced PSII photoinhibition.
- Taxon
- watermelonCitrullus lanatust0
- Treatment
- low irradiancee0
- Outcome
- photoinhibition of PS II photochemistrye0
- Direction
- alleviatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the low irradiance could help to alleviate the extent of photoinhibition of PS II photochemistry caused by chilling”
t0“watermelon”
Claim · model-written summary
ZJ8424 was more temperature-sensitive than YS01.
- Taxon
- watermelonCitrullus lanatust0
- Material
- ZJ8424e0
- Outcome
- sensitive to the extreme temperaturese0
- Direction
- more sensitivee0
- Comparator
- YS01e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cv. ZJ8424 was more sensitive to the extreme temperatures than cv. YS01”
t0“watermelon”
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