Abstract
Cytokinin deficiency causes pleiotropic developmental changes such as reduced shoot and increased root growth. It was investigated whether cytokinin-deficient tobacco plants, which overproduce different cytokinin oxidase/dehydrogenase enzymes, show changes in different sink and source parameters, which could be causally related to the establishment of the cytokinin deficiency syndrome. Ultrastructural analysis revealed distinct changes in differentiating shoot tissues, including an increased vacuolation and an earlier differentiation of plastids, which showed partially disorganized thylakoid structures later in development. A comparison of the ploidy levels revealed an increased population of cells with a 4C DNA content during early stages of leaf development, indicating an inhibited progression from G2 to mitosis. To compare physiological characteristics of sink leaves, source leaves and roots of wild-type and cytokinin-deficient plants, several photosynthetic parameters, content of soluble sugars, starch and adenylates, as well as activities of enzymes of carbon assimilation and dissimilation were determined. Leaves of cytokinin-deficient plants contained less chlorophyll and non-photochemical quenching of young leaves was increased. However, absorption rate, photosynthetic capacity (F(v)/F(m) and J(CO2 max)) and efficiency (Phi CO(2 app)), as well as the content of soluble sugars, were not strongly altered in source leaves, indicating that chlorophyll is not limiting for photoassimilation and suggesting that source strength did not restrict shoot growth. By contrast, shoot sink tissues showed drastically reduced contents of soluble sugars, decreased activities of vacuolar invertases, and a reduced ATP content. These results strongly support a function of cytokinin in regulating shoot sink strength and its reduction may be a cause of the altered shoot phenotype. Roots of cytokinin-deficient plants contained less sugar compared with wild-type. However, this did not negatively affect glycolysis, ATP content, or root development. It is suggested that cytokinin-mediated regulation of the sink strength differs between roots and shoots.
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Claims 17
Claim · model-written summary
Cytokinin-deficient tobacco shoot tissues show increased vacuolation.
- Taxon
- tobacco
Nicotiana tabacumt0 - Organ / stage
- differentiating shoot tissuese1
- Treatment
- cytokinin-deficiente3
- Outcome
- vacuolatione1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e1“Ultrastructural analysis revealed distinct changes in differentiating shoot tissues, including an increased vacuolation and an earlier differentiation of plastids, which showed partially disorganized thylakoid structures later in development”
e3“Leaves of cytokinin-deficient plants contained less chlorophyll and non-photochemical quenching of young leaves was increased”
Claim · model-written summary
Plastids differentiate earlier in cytokinin-deficient tobacco shoot tissues.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- differentiating shoot tissuese1
- Treatment
- cytokinin-deficiente3
- Outcome
- differentiation of plastidse1
- Direction
- earliere1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e1“Ultrastructural analysis revealed distinct changes in differentiating shoot tissues, including an increased vacuolation and an earlier differentiation of plastids, which showed partially disorganized thylakoid structures later in development”
e3“Leaves of cytokinin-deficient plants contained less chlorophyll and non-photochemical quenching of young leaves was increased”
Claim · model-written summary
Thylakoid structures become partially disorganized later in development in cytokinin-deficient tobacco.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- thylakoid structurese1
- Direction
- partially disorganizede1
- Qualifier
- later in developmente1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e1“Ultrastructural analysis revealed distinct changes in differentiating shoot tissues, including an increased vacuolation and an earlier differentiation of plastids, which showed partially disorganized thylakoid structures later in development”
Claim · model-written summary
Cytokinin-deficient tobacco shows an increased population of cells with 4C DNA content in early leaf development.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- early stages of leaf developmente2
- Outcome
- population of cells with a 4C DNA contente2
- Direction
- increasede2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e2“A comparison of the ploidy levels revealed an increased population of cells with a 4C DNA content during early stages of leaf development, indicating an inhibited progression from G2 to mitosis”
Claim · model-written summary
Cytokinin deficiency inhibits progression from G2 to mitosis in tobacco leaves.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- inhibited progression from G2 to mitosise2
- Qualifier
- 4C DNA contente2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e2“A comparison of the ploidy levels revealed an increased population of cells with a 4C DNA content during early stages of leaf development, indicating an inhibited progression from G2 to mitosis”
Claim · model-written summary
Leaves of cytokinin-deficient tobacco contain less chlorophyll.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- Leavese3
- Treatment
- cytokinin-deficiente3
- Outcome
- chlorophylle3
- Direction
- lesse3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e3“Leaves of cytokinin-deficient plants contained less chlorophyll and non-photochemical quenching of young leaves was increased”
Claim · model-written summary
Non-photochemical quenching of young leaves is increased in cytokinin-deficient tobacco.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- young leavese3
- Treatment
- cytokinin-deficiente3
- Outcome
- non-photochemical quenchinge3
- Direction
- increasede3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e3“Leaves of cytokinin-deficient plants contained less chlorophyll and non-photochemical quenching of young leaves was increased”
Claim · model-written summary
Absorption rate, photosynthetic capacity and efficiency are not strongly altered in source leaves of cytokinin-deficient tobacco.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- source leavese4
- Treatment
- cytokinin-deficiente3
- Outcome
- absorption rate, photosynthetic capacity (F(v)/F(m) and J(CO2 max)) and efficiency (Phi CO(2 app))e4
- Direction
- not strongly alterede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e3“Leaves of cytokinin-deficient plants contained less chlorophyll and non-photochemical quenching of young leaves was increased”
e4“However, absorption rate, photosynthetic capacity (F(v)/F(m) and J(CO2 max)) and efficiency (Phi CO(2 app)), as well as the content of soluble sugars, were not strongly altered in source leaves, indicating that chlorophyll is not limiting for photoassimilation and suggesting that source strength did not restrict shoot growth”
Claim · model-written summary
Soluble sugar content is not strongly altered in source leaves of cytokinin-deficient tobacco.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- source leavese4
- Treatment
- cytokinin-deficiente3
- Outcome
- the content of soluble sugarse4
- Direction
- not strongly alterede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e3“Leaves of cytokinin-deficient plants contained less chlorophyll and non-photochemical quenching of young leaves was increased”
e4“However, absorption rate, photosynthetic capacity (F(v)/F(m) and J(CO2 max)) and efficiency (Phi CO(2 app)), as well as the content of soluble sugars, were not strongly altered in source leaves, indicating that chlorophyll is not limiting for photoassimilation and suggesting that source strength did not restrict shoot growth”
Claim · model-written summary
Chlorophyll is not limiting for photoassimilation in cytokinin-deficient tobacco.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- photoassimilatione4
- Qualifier
- chlorophyll is not limitinge4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e4“However, absorption rate, photosynthetic capacity (F(v)/F(m) and J(CO2 max)) and efficiency (Phi CO(2 app)), as well as the content of soluble sugars, were not strongly altered in source leaves, indicating that chlorophyll is not limiting for photoassimilation and suggesting that source strength did not restrict shoot growth”
Claim · model-written summary
Source strength does not restrict shoot growth in cytokinin-deficient tobacco.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- shoot growthe4
- Qualifier
- source strength did not restricte4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e4“However, absorption rate, photosynthetic capacity (F(v)/F(m) and J(CO2 max)) and efficiency (Phi CO(2 app)), as well as the content of soluble sugars, were not strongly altered in source leaves, indicating that chlorophyll is not limiting for photoassimilation and suggesting that source strength did not restrict shoot growth”
Claim · model-written summary
Shoot sink tissues of cytokinin-deficient tobacco have drastically reduced soluble sugar contents.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- shoot sink tissuese5
- Treatment
- cytokinin-deficiente3
- Outcome
- contents of soluble sugarse5
- Direction
- drastically reducede5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e3“Leaves of cytokinin-deficient plants contained less chlorophyll and non-photochemical quenching of young leaves was increased”
e5“By contrast, shoot sink tissues showed drastically reduced contents of soluble sugars, decreased activities of vacuolar invertases, and a reduced ATP content”
Claim · model-written summary
Shoot sink tissues of cytokinin-deficient tobacco have decreased vacuolar invertase activities.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- shoot sink tissuese5
- Treatment
- cytokinin-deficiente3
- Outcome
- activities of vacuolar invertasese5
- Direction
- decreasede5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e3“Leaves of cytokinin-deficient plants contained less chlorophyll and non-photochemical quenching of young leaves was increased”
e5“By contrast, shoot sink tissues showed drastically reduced contents of soluble sugars, decreased activities of vacuolar invertases, and a reduced ATP content”
Claim · model-written summary
Shoot sink tissues of cytokinin-deficient tobacco have a reduced ATP content.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- shoot sink tissuese5
- Treatment
- cytokinin-deficiente3
- Outcome
- ATP contente5
- Direction
- reducede5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e3“Leaves of cytokinin-deficient plants contained less chlorophyll and non-photochemical quenching of young leaves was increased”
e5“By contrast, shoot sink tissues showed drastically reduced contents of soluble sugars, decreased activities of vacuolar invertases, and a reduced ATP content”
Claim · model-written summary
Roots of cytokinin-deficient tobacco contain less sugar than wild-type.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- Rootse6
- Treatment
- cytokinin-deficient plantse6
- Outcome
- sugare6
- Direction
- lesse6
- Comparator
- wild-typee6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e6“Roots of cytokinin-deficient plants contained less sugar compared with wild-type. However, this did not negatively affect glycolysis, ATP content, or root development”
Claim · model-written summary
Lower root sugar does not negatively affect glycolysis, ATP content or root development in cytokinin-deficient tobacco.
- Taxon
- tobaccoNicotiana tabacumt0
- Treatment
- cytokinin-deficiente6
- Outcome
- glycolysis, ATP content, or root developmente6
- Direction
- did not negatively affecte6
- Comparator
- wild-typee6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e6“Roots of cytokinin-deficient plants contained less sugar compared with wild-type. However, this did not negatively affect glycolysis, ATP content, or root development”
Claim · model-written summary
Cytokinin regulates shoot sink strength, and its reduction may cause the altered shoot phenotype.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- shoot sink strengthe7
- Qualifier
- a cause of the altered shoot phenotypee7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco shoots and roots”
e7“These results strongly support a function of cytokinin in regulating shoot sink strength and its reduction may be a cause of the altered shoot phenotype”
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