Abstract
Trifolium repens L. was grown to test the following hypotheses: when P is deficient (i) N2 fixation decreases as a result of the plant's adaptation to the low N demand, regulated by an N feedback mechanism, and (ii) the decrease in the photosynthetic capacity of the leaves does not limit N2 fixation. Severe P deficiency prevented nodulation or stopped nodule growth when the P deficiency occurred after the plants had formed nodules. At low P, the proportion of whole-plant-N derived from symbiotic N2 fixation decreased, whereas specific N2 fixation increased and compensated partially for poor nodulation. Leaf photosynthesis was reduced under P deficiency due to low Vc,max and Jmax. Poor growth or poor performance of the nodules was not due to C limitation, because (i) the improved photosynthetic performance at elevated pCO2 had no effect on the growth and functioning of the nodules, (ii) starch accumulated in the leaves, particularly under elevated pCO2, and (iii) the concentration of WSC in the nodules was highest under P deficiency. Under severe P deficiency, the concentrations of whole-plant-N and leaf-N were the highest, indicating that the assimilation of N exceeded the amount of N required by the plant for growth. This was clearly demonstrated by a strong increase in asparagine concentrations in the roots and nodules under low P supply. This indicates that nodulation and the proportion of N derived from symbiotic N2 fixation are down-regulated by an N feedback mechanism.
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Claims 13
Claim · model-written summary
Severe P deficiency prevented nodulation or stopped existing nodule growth.
- Taxon
- Trifolium repens L.
Trifolium repenst0 - Treatment
- Severe P deficiencye0
- Outcome
- nodulation or stopped nodule growthe0
- Direction
- preventede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Severe P deficiency prevented nodulation or stopped nodule growth when the P deficiency occurred after the plants had formed nodules”
t0“white clover (Trifolium repens L.)”
Claim · model-written summary
Low P decreased the whole-plant N fraction from symbiotic fixation.
- Taxon
- Trifolium repens L.Trifolium repenst0
- Treatment
- low Pe0
- Outcome
- proportion of whole-plant-N derived from symbiotic N2 fixatione0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At low P, the proportion of whole-plant-N derived from symbiotic N2 fixation decreased”
t0“white clover (Trifolium repens L.)”
Claim · model-written summary
Specific N2 fixation increased at low P and partly compensated for poor nodulation.
- Taxon
- Trifolium repens L.Trifolium repenst0
- Treatment
- low Pe1
- Outcome
- specific N2 fixatione0
- Direction
- increasede0
- Qualifier
- compensated partially for poor nodulatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“whereas specific N2 fixation increased and compensated partially for poor nodulation”
e1“At low P”
t0“white clover (Trifolium repens L.)”
Claim · model-written summary
P deficiency reduced leaf photosynthesis with low Vc,max and Jmax.
- Taxon
- Trifolium repens L.Trifolium repenst0
- Treatment
- P deficiencye0
- Outcome
- Leaf photosynthesise0
- Direction
- reducede0
- Qualifier
- low Vc,max and Jmaxe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf photosynthesis was reduced under P deficiency due to low Vc,max and Jmax”
t0“white clover (Trifolium repens L.)”
Claim · model-written summary
Elevated pCO2 improved photosynthetic performance.
- Taxon
- Trifolium repens L.Trifolium repenst0
- Treatment
- elevated pCO2e0
- Outcome
- photosynthetic performancee0
- Direction
- improvede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the improved photosynthetic performance at elevated pCO2 had no effect on the growth and functioning of the nodules”
t0“white clover (Trifolium repens L.)”
Claim · model-written summary
Elevated pCO2 did not affect nodule growth or functioning.
- Taxon
- Trifolium repens L.Trifolium repenst0
- Treatment
- elevated pCO2e0
- Outcome
- growth and functioning of the nodulese0
- Direction
- no effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the improved photosynthetic performance at elevated pCO2 had no effect on the growth and functioning of the nodules”
t0“white clover (Trifolium repens L.)”
Claim · model-written summary
Starch accumulated in leaves, particularly under elevated pCO2.
- Taxon
- Trifolium repens L.Trifolium repenst0
- Organ / stage
- leavese0
- Treatment
- elevated pCO2e0
- Outcome
- starch accumulatede0
- Direction
- accumulatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“starch accumulated in the leaves, particularly under elevated pCO2”
t0“white clover (Trifolium repens L.)”
Claim · model-written summary
Nodule WSC concentration was highest under P deficiency.
- Taxon
- Trifolium repens L.Trifolium repenst0
- Organ / stage
- nodulese0
- Treatment
- P deficiencye0
- Outcome
- concentration of WSCe0
- Direction
- higheste0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the concentration of WSC in the nodules was highest under P deficiency”
t0“white clover (Trifolium repens L.)”
Claim · model-written summary
Whole-plant N concentration was highest under severe P deficiency.
- Taxon
- Trifolium repens L.Trifolium repenst0
- Treatment
- severe P deficiencye0
- Outcome
- concentrations of whole-plant-Ne0
- Direction
- higheste0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under severe P deficiency, the concentrations of whole-plant-N and leaf-N were the highest”
t0“white clover (Trifolium repens L.)”
Claim · model-written summary
Leaf N concentration was highest under severe P deficiency.
- Taxon
- Trifolium repens L.Trifolium repenst0
- Treatment
- severe P deficiencye0
- Outcome
- leaf-Ne0
- Direction
- higheste0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under severe P deficiency, the concentrations of whole-plant-N and leaf-N were the highest”
t0“white clover (Trifolium repens L.)”
Claim · model-written summary
Low P supply strongly increased asparagine concentrations in roots.
- Taxon
- Trifolium repens L.Trifolium repenst0
- Organ / stage
- rootse0
- Treatment
- low P supplye0
- Outcome
- asparagine concentrationse0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a strong increase in asparagine concentrations in the roots and nodules under low P supply”
t0“white clover (Trifolium repens L.)”
Claim · model-written summary
Low P supply strongly increased asparagine concentrations in nodules.
- Taxon
- Trifolium repens L.Trifolium repenst0
- Organ / stage
- nodulese0
- Treatment
- low P supplye0
- Outcome
- asparagine concentrationse0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a strong increase in asparagine concentrations in the roots and nodules under low P supply”
t0“white clover (Trifolium repens L.)”
Claim · model-written summary
N feedback was inferred to downregulate nodulation and N derived from fixation.
- Taxon
- Trifolium repens L.Trifolium repenst0
- Outcome
- nodulation and the proportion of N derived from symbiotic N2 fixatione0
- Direction
- down-regulatede0
- Qualifier
- N feedback mechanisme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This indicates that nodulation and the proportion of N derived from symbiotic N2 fixation are down-regulated by an N feedback mechanism”
t0“white clover (Trifolium repens L.)”
The same questions in other papers
phosphorus · physiology: photosynthesis · Trifolium repens (white clover)Positive and negative results
2 papers in the same direction as this paper · 1 in the opposite direction
This paper is about lacking the nutrient, so it counts the other way round here.
- negative
- positive
- positive
phosphorus · symbiosis · Trifolium repens (white clover)Positive and negative results
6 papers in the same direction as this paper · 2 in the opposite direction
- positive
- positive
- no effect
5 papers more in this group
See all 9 papers →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.