Abstract
Low phosphorus availability is often a primary constraint to plant productivity in native soils. Here we test the hypothesis that root carbon costs are a primary limitation to plant growth in low P soils by assessing the effect of P availability and mycorrhizal infection on whole plant C budgets in common bean ( Phaseolus vulgaris L.). Plants were grown in solid‐phase‐buffered silica sand providing a constant supply of low (1 μ m ) or moderate (10 μ m ) P. Carbon budgets were determined weekly during the vegetative growth phase. Mycorrhizal infection in low‐P plants increased the root specific P absorption rate, but a concurrent increase in root respiration consumed the increased net C gain resulting from greater P uptake. The energy content of mycorrhizal and non‐mycorrhizal roots was similar. We propose that the increase in root respiration in mycorrhizal roots was mainly due to increased maintenance and growth respiration of the fungal tissue. Plants grown with low P availability expended a significantly larger fraction of their total daily C budget on below‐ground respiration at days 21, 28 and 35 after planting (29–40%) compared with plants grown with moderate P supply (18–25%). Relatively greater below‐ground respiration in low P plants was mainly a result of their increased root∶shoot ratio, although specific assimilation rate was reduced significantly at days 21 and 28 after planting. Specific root respiration was reduced over time by low P availability, by up to 40%. This reduction in specific root respiration was due to a reduction in ion uptake respiration and growth respiration, whereas maintenance respiration was increased in low‐P plants. Our results support the hypothesis that root C costs are a primary limitation to plant growth in low‐P soils.
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Claims 11
Claim · model-written summary
Mycorrhizal infection increased root specific phosphorus absorption in low P bean plants.
- Taxon
- common bean
Phaseolus vulgarist0 - Organ / stage
- roote0
- Treatment
- Mycorrhizal infectione0
- Outcome
- root specific P absorption ratee0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Mycorrhizal infection in low‐P plants increased the root specific P absorption rate”
t0“common bean”
Claim · model-written summary
In low P plants, a concurrent rise in root respiration consumed increased net carbon gain from phosphorus uptake.
- Taxon
- common beanPhaseolus vulgarist0
- Organ / stage
- roote0
- Outcome
- net C gaine0
- Qualifier
- increase in root respiratione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a concurrent increase in root respiration consumed the increased net C gain resulting from greater P uptake.”
t0“common bean”
Claim · model-written summary
Mycorrhizal and nonmycorrhizal roots had similar energy content.
- Taxon
- common beanPhaseolus vulgarist0
- Outcome
- energy contente0
- Direction
- similare0
- Comparator
- non‐mycorrhizal rootse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The energy content of mycorrhizal and non‐mycorrhizal roots was similar.”
t0“common bean”
Claim · model-written summary
The authors attribute increased root respiration in mycorrhizal roots mainly to fungal maintenance and growth respiration.
- Taxon
- common beanPhaseolus vulgarist0
- Outcome
- root respiratione0
- Qualifier
- increased maintenance and growth respiration of the fungal tissuee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We propose that the increase in root respiration in mycorrhizal roots was mainly due to increased maintenance and growth respiration of the fungal tissue.”
t0“common bean”
Claim · model-written summary
Low phosphorus plants devoted a larger share of daily carbon budget to below ground respiration than moderate phosphorus plants on days 21, 28 and 35.
- Taxon
- common beanPhaseolus vulgarist0
- Treatment
- low P availabilitye0
- Outcome
- fraction of their total daily C budget on below‐ground respiratione0
- Direction
- largere0
- Value
- 29–40%e0
- Qualifier
- days 21, 28 and 35 after planting (29–40%)e0
- Comparator
- moderate P supplye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plants grown with low P availability expended a significantly larger fraction of their total daily C budget on below‐ground respiration at days 21, 28 and 35 after planting (29–40%) compared with plants grown with moderate P supply (18–25%).”
t0“common bean”
Claim · model-written summary
The relatively greater below ground respiration under low phosphorus was mainly attributed to increased root to shoot ratio.
- Taxon
- common beanPhaseolus vulgarist0
- Outcome
- below‐ground respiratione0
- Qualifier
- increased root∶shoot ratioe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Relatively greater below‐ground respiration in low P plants was mainly a result of their increased root∶shoot ratio”
t0“common bean”
Claim · model-written summary
Specific assimilation rate was significantly reduced at 21 and 28 days after planting.
- Taxon
- common beanPhaseolus vulgarist0
- Outcome
- specific assimilation ratee0
- Direction
- reducede0
- Qualifier
- days 21 and 28 after plantinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“specific assimilation rate was reduced significantly at days 21 and 28 after planting.”
t0“common bean”
Claim · model-written summary
Low phosphorus reduced specific root respiration over time by up to 40%.
- Taxon
- common beanPhaseolus vulgarist0
- Treatment
- low P availabilitye0
- Outcome
- Specific root respiratione0
- Direction
- reducede0
- Value
- 40%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Specific root respiration was reduced over time by low P availability, by up to 40%.”
t0“common bean”
Claim · model-written summary
The reduction in specific root respiration reflected reduced ion uptake respiration and growth respiration.
- Taxon
- common beanPhaseolus vulgarist0
- Outcome
- specific root respiratione0
- Qualifier
- reduction in ion uptake respiration and growth respiratione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This reduction in specific root respiration was due to a reduction in ion uptake respiration and growth respiration”
t0“common bean”
Claim · model-written summary
Maintenance respiration increased in low phosphorus plants.
- Taxon
- common beanPhaseolus vulgarist0
- Treatment
- low‐Pe0
- Outcome
- maintenance respiratione0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maintenance respiration was increased in low‐P plants.”
t0“common bean”
Claim · model-written summary
The authors conclude root carbon costs primarily limit growth in low phosphorus soil.
- Taxon
- common beanPhaseolus vulgarist0
- Outcome
- plant growthe0
- Qualifier
- root C costs are a primary limitatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Our results support the hypothesis that root C costs are a primary limitation to plant growth in low‐P soils.”
t0“common bean”
The same questions in other papers
infection · nutrient: content · Phaseolus vulgaris (common bean)Positive and negative results
2 in the opposite direction
- no effect
- negative
mycorrhiza · nutrient: content · Phaseolus vulgaris (common bean)Results agree
11 papers in the same direction as this paper
- positive
- positive
- positive
8 papers more in this group
See all 12 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.