Abstract
BACKGROUND AND AIMS: Chilling results in a significant decrease in Rubisco content and increased generation of reactive oxygen species (ROS) in cucumber (Cucumis sativus), a chilling-sensitive species. The role of roots in the regulation of the tolerance is unknown. Here, cucumber plants grafted onto figleaf gourd (Cucurbita ficifolia), a chilling-tolerant species were used to study the role of roots in the regulation of shoot functioning and the associated root-to-shoot communication. METHODS: Gas exchange and chlorophyll fluorescence were measured using an infrared gas analyser combined with a pulse amplitude fluorimeter during chilling at 14 degrees C or 7 degrees C and subsequent recovery. At the same time, Rubisco content and activity and ROS generation were spectrophotometrically assayed. Abscisic acid and cytokinin concentrations in xylem sap were also determined by enzyme-linked immunosorbent assay. KEY RESULTS AND CONCLUSIONS: Grafted plants showed a significantly higher light-saturated rate of CO(2) assimilation (A(sat)) than own-rooted plants when roots were gradually cooled, but no differences were detected when shoots were cooled. Chill at 7 degrees C irreversibly reduced A(sat), and significantly decreased maximum carboxylation activity, Rubisco content and initial Rubisco activity. However, grafted plants showed weaker inhibition, together with decreased electron flux in the water-water cycle. Higher activity of antioxidant enzymes with less ROS production was found in grafted plants. In addition, ABA concentration increased by 48.4-fold whilst cytokinin concentration decreased by 91.5% in the xylem sap of own-rooted plants after exposure to a 7 degrees C chill. In comparison, ABA and cytokinin concentrations increased by 10.5-fold and 36.9%, respectively, for the grafted plants. Improved plant growth was also observed in grafted plants after the chill. These results suggest that some signals coming from chilling-resistant roots (i.e. ABA and cytokinins) protect leaf photosynthesis in shoots of chilling-sensitive plants.
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Claims 11
Claim · model-written summary
Grafted cucumber had significantly higher light-saturated CO2 assimilation than own-rooted plants during gradual root cooling.
- Taxon
- cucumber
Cucumis sativuse1 - Treatment
- grafted onto figleaf gourde1
- Outcome
- light-saturated rate of CO(2) assimilation (A(sat))e0
- Direction
- highere0
- Qualifier
- when roots were gradually coolede0
- Comparator
- own-rooted plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grafted plants showed a significantly higher light-saturated rate of CO(2) assimilation (A(sat)) than own-rooted plants when roots were gradually cooled”
e1“cucumber plants grafted onto figleaf gourd”
Claim · model-written summary
Grafted and own-rooted cucumber did not differ in assimilation when shoots were cooled.
- Taxon
- cucumberCucumis sativuse1
- Treatment
- grafted onto figleaf gourde1
- Outcome
- light-saturated rate of CO(2) assimilation (A(sat))e2
- Direction
- no differencese0
- Qualifier
- when shoots were coolede0
- Comparator
- own-rooted plantse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“no differences were detected when shoots were cooled”
e1“cucumber plants grafted onto figleaf gourd”
e2“light-saturated rate of CO(2) assimilation (A(sat)) than own-rooted plants”
Claim · model-written summary
Chilling at 7 degrees C irreversibly reduced cucumber assimilation.
- Taxon
- cucumberCucumis sativuse1
- Treatment
- Chill at 7 degrees Ce0
- Outcome
- A(sat)e0
- Direction
- reducede0
- Qualifier
- irreversiblye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Chill at 7 degrees C irreversibly reduced A(sat)”
e1“cucumber (Cucumis sativus)”
Claim · model-written summary
Chilling at 7 degrees C significantly decreased maximum carboxylation activity, Rubisco content and initial Rubisco activity.
- Taxon
- cucumberCucumis sativuse1
- Treatment
- Chill at 7 degrees Ce0
- Outcome
- maximum carboxylation activity, Rubisco content and initial Rubisco activitye0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Chill at 7 degrees C irreversibly reduced A(sat), and significantly decreased maximum carboxylation activity, Rubisco content and initial Rubisco activity.”
e1“cucumber (Cucumis sativus)”
Claim · model-written summary
Grafting weakened chilling inhibition and reduced electron flux in the water-water cycle.
- Taxon
- cucumberCucumis sativuse1
- Treatment
- grafted onto figleaf gourde1
- Outcome
- electron flux in the water-water cyclee0
- Direction
- decreasede0
- Comparator
- own-rooted plantse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“grafted plants showed weaker inhibition, together with decreased electron flux in the water-water cycle”
e1“cucumber plants grafted onto figleaf gourd”
e2“than own-rooted plants when roots were gradually cooled”
Claim · model-written summary
Grafted cucumber had higher antioxidant enzyme activity and less ROS production.
- Taxon
- cucumberCucumis sativuse1
- Treatment
- grafted onto figleaf gourde1
- Outcome
- activity of antioxidant enzymese0
- Direction
- Highere0
- Comparator
- own-rooted plantse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Higher activity of antioxidant enzymes with less ROS production was found in grafted plants.”
e1“cucumber plants grafted onto figleaf gourd”
e2“than own-rooted plants when roots were gradually cooled”
Claim · model-written summary
Own-rooted cucumber xylem ABA increased 48.4-fold after 7 degrees C chilling.
- Taxon
- cucumberCucumis sativuse1
- Organ / stage
- xylem sape0
- Treatment
- 7 degrees C chille0
- Outcome
- ABA concentratione0
- Direction
- increasede0
- Value
- 48.4-folde0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA concentration increased by 48.4-fold whilst cytokinin concentration decreased by 91.5% in the xylem sap of own-rooted plants after exposure to a 7 degrees C chill”
e1“cucumber (Cucumis sativus)”
Claim · model-written summary
Own-rooted cucumber xylem cytokinin decreased 91.5% after chilling.
- Taxon
- cucumberCucumis sativuse1
- Organ / stage
- xylem sape0
- Treatment
- 7 degrees C chille0
- Outcome
- cytokinin concentratione0
- Direction
- decreasede0
- Value
- 91.5%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA concentration increased by 48.4-fold whilst cytokinin concentration decreased by 91.5% in the xylem sap of own-rooted plants after exposure to a 7 degrees C chill”
e1“cucumber (Cucumis sativus)”
Claim · model-written summary
Grafted cucumber xylem ABA increased 10.5-fold after chilling.
- Taxon
- cucumberCucumis sativuse1
- Treatment
- grafted onto figleaf gourde1
- Outcome
- ABAe0
- Direction
- increasede0
- Value
- 10.5-folde0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA and cytokinin concentrations increased by 10.5-fold and 36.9%, respectively, for the grafted plants”
e1“cucumber plants grafted onto figleaf gourd”
Claim · model-written summary
Grafted cucumber xylem cytokinin increased 36.9% after chilling.
- Taxon
- cucumberCucumis sativuse1
- Treatment
- grafted onto figleaf gourde1
- Outcome
- cytokinin concentrationse0
- Direction
- increasede0
- Value
- 36.9%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA and cytokinin concentrations increased by 10.5-fold and 36.9%, respectively, for the grafted plants”
e1“cucumber plants grafted onto figleaf gourd”
Claim · model-written summary
Grafted cucumber grew better after chilling.
- Taxon
- cucumberCucumis sativuse1
- Treatment
- grafted onto figleaf gourde1
- Outcome
- plant growthe0
- Direction
- Improvede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Improved plant growth was also observed in grafted plants after the chill”
e1“cucumber plants grafted onto figleaf gourd”
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