Abstract
Striga hermonthica is a root hemiparasitic angiosperm native to the African semi-arid tropics. It is a major weed of C4 cereals but locally it is also an important weed of the C3 plant, rice [Oryza sativa). Infected rice plants produced 17% and 42% of the total biomass of uninfected plants when grown at two different ammonium nitrate concentrations, 1 and 3 mol m−3, respectively. S. hermonthica prevented grain production at both concentrations of nitrogen. At the lower concentration no heads were produced. At the higher concentration head weight was only 6% of uninfected controls. S. hermonthica also altered the partitioning of dry matter between plant parts, such that shoot growth was reduced to a greater extent than root growth. As a consequence the root-to-shoot ratio of infected plants was approximately five times greater than that of uninfected control plants. Light saturated rates of photosynthesis In infected plants were 56% and 70% of those of uninfected controls, at low and high nitrogen, respectively. Infection also led to lower values of stomatal conductance although the substom-atal CO2 concentration was unaffected. Analysis of the response of photosynthesis to substomatal CO2 concentration (A/CI curves) demonstrated that lower rates of photosynthesis could not be solely attributed to lower stomatal conductances. Lower initial slopes and asymptotic rates suggest that both carboxylation and processes controlling regeneration of ribulose-1, 5-bisphosphate are reduced by infection. The data are discussed with respect to the influence of S. hermonthica on the growth and photosynthesis of C4 hosts, where in contrast to the situation with rice, nitrogen feeding results in a marked alleviation of the effects of the parasite on the host.
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Claims 13
Claim · model-written summary
Infected rice biomass was 17% of uninfected plants at 1 mol m−3 ammonium nitrate.
- Taxon
- rice
Oryza sativae0 - Treatment
- Infectede0
- Interactor
- Striga hermonthica
Striga hermonthicat0parasite - Outcome
- total biomasse0
- Direction
- 17%e0
- Value
- 17%e0
- Qualifier
- 1 and 3 mol m−3e0
- Comparator
- uninfected plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Infected rice plants produced 17% and 42% of the total biomass of uninfected plants when grown at two different ammonium nitrate concentrations, 1 and 3 mol m−3, respectively.”
t0“Striga hermonthica”
Claim · model-written summary
Infected rice biomass was 42% of uninfected plants at 3 mol m−3 ammonium nitrate.
- Taxon
- riceOryza sativae0
- Treatment
- Infectede0
- Interactor
- Striga hermonthicaStriga hermonthicat0parasite
- Outcome
- total biomasse0
- Direction
- 42%e0
- Value
- 42%e0
- Qualifier
- 1 and 3 mol m−3e0
- Comparator
- uninfected plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Infected rice plants produced 17% and 42% of the total biomass of uninfected plants when grown at two different ammonium nitrate concentrations, 1 and 3 mol m−3, respectively.”
t0“Striga hermonthica”
Claim · model-written summary
Striga prevented grain production at both nitrogen concentrations.
- Taxon
- Oryza sativaOryza sativat0
- Treatment
- S. hermonthicae0
- Interactor
- S. hermonthicaStriga hermonthicae0parasite
- Outcome
- grain productione0
- Direction
- preventede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“S. hermonthica prevented grain production at both concentrations of nitrogen.”
t0“Oryza sativa”
Claim · model-written summary
At lower nitrogen, infected rice produced no heads.
- Taxon
- Oryza sativaOryza sativat0
- Outcome
- no heads were producede0
- Qualifier
- lower concentratione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the lower concentration no heads were produced.”
t0“Oryza sativa”
Claim · model-written summary
At higher nitrogen, infected head weight was 6% of uninfected controls.
- Taxon
- Oryza sativaOryza sativat0
- Treatment
- Infectede1
- Outcome
- head weighte0
- Direction
- onlye0
- Value
- 6%e0
- Qualifier
- higher concentratione0
- Comparator
- uninfected controlse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the higher concentration head weight was only 6% of uninfected controls.”
t0“Oryza sativa”
e1“Infected rice plants produced 17% and 42% of the total biomass of uninfected plants when grown at two different ammonium nitrate concentrations, 1 and 3 mol m−3, respectively.”
Claim · model-written summary
Infection reduced shoot growth more than root growth.
- Taxon
- Oryza sativaOryza sativat0
- Treatment
- Infectede1
- Outcome
- shoot growthe0
- Direction
- reducede0
- Comparator
- root growthe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“shoot growth was reduced to a greater extent than root growth.”
t0“Oryza sativa”
e1“Infected rice plants produced 17% and 42% of the total biomass of uninfected plants when grown at two different ammonium nitrate concentrations, 1 and 3 mol m−3, respectively.”
Claim · model-written summary
Infected plants had about five times the root-to-shoot ratio of controls.
- Taxon
- Oryza sativaOryza sativat0
- Treatment
- infectede0
- Outcome
- root-to-shoot ratioe0
- Direction
- greatere0
- Value
- approximately five timese0
- Comparator
- uninfected control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“root-to-shoot ratio of infected plants was approximately five times greater than that of uninfected control plants.”
t0“Oryza sativa”
Claim · model-written summary
Photosynthesis in infected plants was 56% of controls at low nitrogen.
- Taxon
- Oryza sativaOryza sativat0
- Treatment
- infectede0
- Outcome
- Light saturated rates of photosynthesise0
- Value
- 56%e0
- Qualifier
- low and high nitrogene0
- Comparator
- uninfected controlse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Light saturated rates of photosynthesis In infected plants were 56% and 70% of those of uninfected controls, at low and high nitrogen, respectively.”
t0“Oryza sativa”
Claim · model-written summary
Photosynthesis in infected plants was 70% of controls at high nitrogen.
- Taxon
- Oryza sativaOryza sativat0
- Treatment
- infectede0
- Outcome
- Light saturated rates of photosynthesise0
- Value
- 70%e0
- Qualifier
- low and high nitrogene0
- Comparator
- uninfected controlse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Light saturated rates of photosynthesis In infected plants were 56% and 70% of those of uninfected controls, at low and high nitrogen, respectively.”
t0“Oryza sativa”
Claim · model-written summary
Infection lowered stomatal conductance.
- Taxon
- Oryza sativaOryza sativat0
- Treatment
- Infectione0
- Outcome
- stomatal conductancee0
- Direction
- lowere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Infection also led to lower values of stomatal conductance”
t0“Oryza sativa”
Claim · model-written summary
Infection did not change substomatal CO2 concentration.
- Taxon
- Oryza sativaOryza sativat0
- Treatment
- Infectede1
- Outcome
- substom-atal CO2 concentratione0
- Direction
- unaffectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“although the substom-atal CO2 concentration was unaffected.”
t0“Oryza sativa”
e1“Infected rice plants produced 17% and 42% of the total biomass of uninfected plants when grown at two different ammonium nitrate concentrations, 1 and 3 mol m−3, respectively.”
Claim · model-written summary
Lower photosynthesis could not be explained solely by lower stomatal conductance.
- Taxon
- Oryza sativaOryza sativat0
- Outcome
- lower rates of photosynthesise0
- Qualifier
- lower stomatal conductancese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lower rates of photosynthesis could not be solely attributed to lower stomatal conductances.”
t0“Oryza sativa”
Claim · model-written summary
Infection appeared to reduce carboxylation and ribulose-1, 5-bisphosphate regeneration.
- Taxon
- Oryza sativaOryza sativat0
- Treatment
- infectione0
- Outcome
- carboxylation and processes controlling regeneration of ribulose-1, 5-bisphosphatee0
- Direction
- reducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lower initial slopes and asymptotic rates suggest that both carboxylation and processes controlling regeneration of ribulose-1, 5-bisphosphate are reduced by infection.”
t0“Oryza sativa”
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Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.