Abstract
BACKGROUND: Low phosphorus availability is a major factor limiting rice productivity. Since root traits determine phosphorus acquisition efficiency, they are logical selection targets for breeding rice with higher productivity in low phosphorus soils. Before using these traits for breeding, it is necessary to identify genetic variation and to assess the plasticity of each trait in response to the environment. In this study, we measured phenotypic variation and effect of phosphorus deficiency on root architectural, morphological and anatomical traits in 15 rice (Oryza sativa) genotypes. Rice plants were grown with diffusion-limited phosphorus using solid-phase buffered phosphorus to mimic realistic phosphorus availability conditions. RESULTS: Shoot dry weight, tiller number, plant height, number of nodal roots and shoot phosphorus content were reduced under low phosphorus availability. Phosphorus deficiency significantly reduced large lateral root density and small and large lateral root length in all genotypes, though the degree of plasticity and relative allocation of root length between the two root classes varied among genotypes. Root hair length and density increased in all genotypes in response to low phosphorus. Nodal root cross-sectional area was significantly less under low phosphorus availability, and reduced cortical area was disproportionately responsible for this decline. Phosphorus deficiency caused a 20 % increase in the percent cortical area converted to aerenchyma. Total stele area and meta-xylem vessel area responses to low phosphorus differed significantly among genotypes. Phosphorus treatment did not significantly affect theoretical water conductance overall, but increased or reduced it in a few genotypes. All genotypes had restricted water conductance at the base of the nodal root compared to other positions along the root axis. CONCLUSIONS: There was substantial genetic variation for all root traits investigated. Low phosphorus availability significantly affected most traits, often to an extent that varied with the genotype. With the exception of stele and meta-xylem vessel area, root responses to low phosphorus were in the same direction for all genotypes tested. Therefore, phenotypic evaluations conducted with adequate fertility should be useful for genetic mapping studies and identifying potential sources of trait variation, but these should be confirmed in low-phosphorus environments.
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Claims 15
Claim · model-written summary
Low phosphorus reduced rice shoot dry weight, tiller number, and plant height.
- Taxon
- rice (Oryza sativa)
Oryza sativae1 - Treatment
- low phosphorus availabilitye0
- Outcome
- Shoot dry weight, tiller number, plant heighte0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Shoot dry weight, tiller number, plant height, number of nodal roots and shoot phosphorus content were reduced under low phosphorus availability”
e1“rice (Oryza sativa) genotypes”
Claim · model-written summary
Low phosphorus reduced rice nodal root number and shoot phosphorus content.
- Taxon
- rice (Oryza sativa)Oryza sativae1
- Treatment
- low phosphorus availabilitye0
- Outcome
- number of nodal roots and shoot phosphorus contente0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“number of nodal roots and shoot phosphorus content were reduced under low phosphorus availability”
e1“rice (Oryza sativa) genotypes”
Claim · model-written summary
Phosphorus deficiency reduced large lateral root density and both small and large lateral root length in all genotypes.
- Taxon
- rice (Oryza sativa)Oryza sativae1
- Treatment
- Phosphorus deficiencye0
- Outcome
- large lateral root density and small and large lateral root lengthe0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Phosphorus deficiency significantly reduced large lateral root density and small and large lateral root length in all genotypes”
e1“rice (Oryza sativa) genotypes”
Claim · model-written summary
Root length plasticity and allocation between lateral root classes varied among rice genotypes.
- Taxon
- rice (Oryza sativa)Oryza sativae1
- Material
- genotypese0
- Outcome
- degree of plasticity and relative allocation of root lengthe0
- Direction
- variede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the degree of plasticity and relative allocation of root length between the two root classes varied among genotypes”
e1“rice (Oryza sativa) genotypes”
Claim · model-written summary
Low phosphorus increased root hair length and density in every genotype.
- Taxon
- rice (Oryza sativa)Oryza sativae1
- Treatment
- low phosphoruse0
- Outcome
- Root hair length and densitye0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Root hair length and density increased in all genotypes in response to low phosphorus”
e1“rice (Oryza sativa) genotypes”
Claim · model-written summary
Low phosphorus significantly reduced nodal root cross-sectional area.
- Taxon
- rice (Oryza sativa)Oryza sativae1
- Treatment
- low phosphorus availabilitye0
- Outcome
- Nodal root cross-sectional areae0
- Direction
- lesse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nodal root cross-sectional area was significantly less under low phosphorus availability”
e1“rice (Oryza sativa) genotypes”
Claim · model-written summary
Reduced cortical area contributed disproportionately to the nodal root area decline.
- Taxon
- rice (Oryza sativa)Oryza sativae1
- Organ / stage
- cortical areae0
- Outcome
- this declinee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reduced cortical area was disproportionately responsible for this decline”
e1“rice (Oryza sativa) genotypes”
Claim · model-written summary
Phosphorus deficiency increased cortical area converted to aerenchyma by 20 %.
- Taxon
- rice (Oryza sativa)Oryza sativae1
- Treatment
- Phosphorus deficiencye0
- Outcome
- percent cortical area converted to aerenchymae0
- Direction
- increasee0
- Value
- 20 %e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Phosphorus deficiency caused a 20 % increase in the percent cortical area converted to aerenchyma”
e1“rice (Oryza sativa) genotypes”
Claim · model-written summary
Stele area and meta-xylem vessel area responses differed among genotypes.
- Taxon
- rice (Oryza sativa)Oryza sativae1
- Material
- genotypese0
- Outcome
- Total stele area and meta-xylem vessel area responsese0
- Direction
- differede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Total stele area and meta-xylem vessel area responses to low phosphorus differed significantly among genotypes”
e1“rice (Oryza sativa) genotypes”
Claim · model-written summary
Phosphorus treatment had no significant overall effect on theoretical water conductance.
- Taxon
- rice (Oryza sativa)Oryza sativae1
- Treatment
- Phosphorus treatmente0
- Outcome
- theoretical water conductancee0
- Direction
- did not significantly affecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Phosphorus treatment did not significantly affect theoretical water conductance overall”
e1“rice (Oryza sativa) genotypes”
Claim · model-written summary
Phosphorus treatment increased theoretical water conductance in a few genotypes.
- Taxon
- rice (Oryza sativa)Oryza sativae2
- Outcome
- theoretical water conductancee1
- Direction
- increasede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased or reduced it in a few genotypes”
e1“theoretical water conductance overall”
e2“rice (Oryza sativa) genotypes”
Claim · model-written summary
Phosphorus treatment reduced theoretical water conductance in a few genotypes.
- Taxon
- rice (Oryza sativa)Oryza sativae2
- Outcome
- theoretical water conductancee1
- Direction
- reducede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased or reduced it in a few genotypes”
e1“theoretical water conductance overall”
e2“rice (Oryza sativa) genotypes”
Claim · model-written summary
All rice genotypes had restricted water conductance at the nodal root base relative to other positions.
- Taxon
- rice (Oryza sativa)Oryza sativae1
- Organ / stage
- base of the nodal roote0
- Outcome
- restricted water conductancee0
- Comparator
- other positions along the root axise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“All genotypes had restricted water conductance at the base of the nodal root compared to other positions along the root axis”
e1“rice (Oryza sativa) genotypes”
Claim · model-written summary
All investigated rice root traits showed substantial genetic variation.
- Taxon
- rice (Oryza sativa)Oryza sativae1
- Outcome
- genetic variation for all root traits investigatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There was substantial genetic variation for all root traits investigated”
e1“rice (Oryza sativa) genotypes”
Claim · model-written summary
The authors recommend confirming adequately fertilized phenotypic evaluations in low-phosphorus environments.
- Taxon
- rice (Oryza sativa)Oryza sativae1
- Outcome
- these should be confirmed in low-phosphorus environmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“phenotypic evaluations conducted with adequate fertility should be useful for genetic mapping studies and identifying potential sources of trait variation, but these should be confirmed in low-phosphorus environments”
e1“rice (Oryza sativa) genotypes”
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