Abstract
The mechanism of age-induced decreased stomatal sensitivity to abscisic acid (ABA) and soil drying has been explored here. Older, fully expanded leaves partly lost their ability to close stomata in response to foliar ABA sprays, and soil drying which stimulated endogenous ABA production, while young fully expanded leaves closed their stomata more fully. However, ABA- or soil drying-induced stomatal closure of older leaves was partly restored by pretreating plants with 1-methylcyclopropene (1-MCP), which can antagonize ethylene receptors, or by inoculating soil around the roots with the rhizobacterium Variovorax paradoxus 5C-2, which contains 1-aminocyclopropane-1-carboxylic acid (ACC)-deaminase. ACC (the immediate biosynthetic precursor of ethylene) sprays revealed higher sensitivity of stomata to ethylene in older leaves than younger leaves, despite no differences in endogenous ACC concentrations or ethylene emission. Taken together, these results indicate that the relative insensitivity of stomatal closure to ABA and soil drying in older leaves is likely due to altered stomatal sensitivity to ethylene, rather than ethylene production. To our knowledge, this is the first study to mechanistically explain diminished stomatal responses to soil moisture deficit in older leaves, and the associated reduction in leaf water-use efficiency.
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Claims 8
Claim · model-written summary
Older leaves closed stomata less fully than young leaves after ABA sprays.
- Taxon
- wheat
Triticum aestivumt0 - Organ / stage
- Older, fully expanded leavese0
- Treatment
- foliar ABA sprayse0
- Outcome
- ability to close stomatae0
- Direction
- partly loste0
- Comparator
- young fully expanded leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Older, fully expanded leaves partly lost their ability to close stomata in response to foliar ABA sprays, and soil drying which stimulated endogenous ABA production, while young fully expanded leaves closed their stomata more fully”
t0“wheat”
Claim · model-written summary
Older leaves closed stomata less fully than young leaves during soil drying.
- Taxon
- wheatTriticum aestivumt0
- Organ / stage
- Older, fully expanded leavese0
- Treatment
- soil dryinge0
- Outcome
- ability to close stomatae0
- Direction
- partly loste0
- Comparator
- young fully expanded leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Older, fully expanded leaves partly lost their ability to close stomata in response to foliar ABA sprays, and soil drying which stimulated endogenous ABA production, while young fully expanded leaves closed their stomata more fully”
t0“wheat”
Claim · model-written summary
1-MCP partly restored ABA or drying induced stomatal closure in older leaves.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- 1-methylcyclopropene (1-MCP)e0
- Outcome
- ABA- or soil drying-induced stomatal closure of older leavese0
- Direction
- partly restorede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA- or soil drying-induced stomatal closure of older leaves was partly restored by pretreating plants with 1-methylcyclopropene (1-MCP)”
t0“wheat”
Claim · model-written summary
Variovorax paradoxus 5C-2 partly restored ABA or drying induced stomatal closure in older leaves.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- inoculating soil around the roots with the rhizobacterium Variovorax paradoxus 5C-2e0
- Interactor
- Variovorax paradoxus 5C-2Variovorax paradoxuse0symbiont
- Outcome
- ABA- or soil drying-induced stomatal closure of older leavese0
- Direction
- partly restorede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA- or soil drying-induced stomatal closure of older leaves was partly restored by pretreating plants with 1-methylcyclopropene (1-MCP), which can antagonize ethylene receptors, or by inoculating soil around the roots with the rhizobacterium Variovorax paradoxus 5C-2”
t0“wheat”
Claim · model-written summary
Older leaf stomata were more ethylene sensitive than younger leaf stomata.
- Taxon
- wheatTriticum aestivumt0
- Organ / stage
- older leavese0
- Outcome
- sensitivity of stomata to ethylenee0
- Direction
- highere0
- Comparator
- younger leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ACC (the immediate biosynthetic precursor of ethylene) sprays revealed higher sensitivity of stomata to ethylene in older leaves than younger leaves”
t0“wheat”
Claim · model-written summary
Endogenous ACC concentrations did not differ between older and younger leaves.
- Taxon
- wheatTriticum aestivumt0
- Organ / stage
- older leavese1
- Outcome
- endogenous ACC concentrationse0
- Direction
- no differencese0
- Comparator
- younger leavese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“despite no differences in endogenous ACC concentrations or ethylene emission”
e1“in older leaves than younger leaves”
t0“wheat”
Claim · model-written summary
Ethylene emission did not differ between older and younger leaves.
- Taxon
- wheatTriticum aestivumt0
- Organ / stage
- older leavese1
- Outcome
- ethylene emissione0
- Direction
- no differencese0
- Comparator
- younger leavese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“despite no differences in endogenous ACC concentrations or ethylene emission”
e1“in older leaves than younger leaves”
t0“wheat”
Claim · model-written summary
Altered ethylene sensitivity likely explains weaker ABA and drying stomatal responses in older leaves.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- relative insensitivity of stomatal closure to ABA and soil drying in older leavese0
- Qualifier
- altered stomatal sensitivity to ethylenee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the relative insensitivity of stomatal closure to ABA and soil drying in older leaves is likely due to altered stomatal sensitivity to ethylene”
t0“wheat”
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