Abstract
Young sunflower plants (Helianthus annuus L.) under stress of low nitrate or phosphate availability exhibited increases in root: shoot ratio and in kinetic parameters for uptake. They showed no significant changes in photosynthetic utilization of either nutrient. Increases in root: shoot ratio were achieved by early and persistent suppression of shoot growth, but not root growth. Affinity for phosphate uptake, 1/Km(P), increased with phosphate stress, as did affinity for nitrate uptake, 1/Km(N), with nitrate stress. Maximal uptake rate, Vmax, for phosphate uptake increased with phosphorus stress; Vmax for nitrate did not increase with nitrogen stress. Phosphate Vmax was related strongly to root nutrient status. Decreases in Vmax with plant age were not well explained by changes in age structure of roots. Estimated benefits of acclimatory changes in root: shoot ratio and uptake kinetics ranged up to 2-fold increases in relative growth rate, RGR. The relation of RGR to uptake physiology followed predictions of functional balance moderately well, with some systematic deviations. Analyses of RGR using growth models imply no significant growth benefit from regulating Vmax, specifically, not from down-regulating it at high nutrient availability. Quantitative benefits of increases in root: shoot ratio and uptake parameters are predicted to be quite small under common conditions wherein nutrient concentrations are significantly depleted by uptake. The root: shoot response is estimated to confer the smallest benefit under non-depleting conditions and the largest benefit under depleting conditions. Even then, the absolute benefit is predicted to be small, possibly excepting the case of heterogeneous soils. Depleting and non-depleting conditions are addressed with very different experimental techniques. We note that a theoretical framework is lacking that spans both these cases, other than purely numerical formulations that are not readily interpreted.
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Claims 15
Claim · model-written summary
Low nitrate or phosphate increased root:shoot ratio and uptake kinetic parameters.
- Taxon
- sunflower plants (Helianthus annuus L.)
Helianthus annuust0 - Treatment
- low nitrate or phosphate availabilitye0
- Outcome
- root: shoot ratio and in kinetic parameters for uptakee0
- Direction
- increasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“under stress of low nitrate or phosphate availability exhibited increases in root: shoot ratio and in kinetic parameters for uptake”
Claim · model-written summary
Nutrient limitation did not significantly change photosynthetic utilization of either nutrient.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Outcome
- photosynthetic utilization of either nutriente0
- Direction
- no significant changese0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“no significant changes in photosynthetic utilization of either nutrient”
Claim · model-written summary
Higher root:shoot ratio resulted from early sustained suppression of shoot growth, not root growth.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Organ / stage
- shoot growthe0
- Outcome
- root: shoot ratioe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“Increases in root: shoot ratio were achieved by early and persistent suppression of shoot growth, but not root growth”
Claim · model-written summary
Phosphate stress increased phosphate uptake affinity.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Treatment
- phosphate stresse0
- Outcome
- Affinity for phosphate uptake, 1/Km(P)e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“Affinity for phosphate uptake, 1/Km(P), increased with phosphate stress”
Claim · model-written summary
Nitrate stress increased nitrate uptake affinity.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Treatment
- nitrate stresse0
- Outcome
- affinity for nitrate uptake, 1/Km(N)e0
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“affinity for nitrate uptake, 1/Km(N), with nitrate stress”
e1“increased with phosphate stress, as did affinity for nitrate uptake, 1/Km(N), with nitrate stress”
Claim · model-written summary
Phosphorus stress increased maximum phosphate uptake rate.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Treatment
- phosphorus stresse0
- Outcome
- Maximal uptake rate, Vmax, for phosphate uptakee0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“Maximal uptake rate, Vmax, for phosphate uptake increased with phosphorus stress”
Claim · model-written summary
Nitrogen stress did not increase maximum nitrate uptake rate.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Treatment
- nitrogen stresse0
- Outcome
- Vmax for nitratee0
- Direction
- did not increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“Vmax for nitrate did not increase with nitrogen stress”
Claim · model-written summary
Phosphate Vmax was strongly related to root nutrient status.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Organ / stage
- root nutrient statuse0
- Outcome
- Phosphate Vmaxe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“Phosphate Vmax was related strongly to root nutrient status”
Claim · model-written summary
Changes in root age structure poorly explained age-related Vmax decreases.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Organ / stage
- age structure of rootse0
- Outcome
- Vmaxe0
- Direction
- Decreasese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“Decreases in Vmax with plant age were not well explained by changes in age structure of roots”
Claim · model-written summary
Estimated acclimation benefits reached twofold increases in relative growth rate.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Outcome
- relative growth rate, RGRe0
- Direction
- increasese0
- Value
- 2-folde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“Estimated benefits of acclimatory changes in root: shoot ratio and uptake kinetics ranged up to 2-fold increases in relative growth rate, RGR”
Claim · model-written summary
The RGR relationship to uptake physiology moderately matched functional balance predictions with systematic deviations.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Outcome
- relation of RGR to uptake physiologye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“The relation of RGR to uptake physiology followed predictions of functional balance moderately well, with some systematic deviations”
Claim · model-written summary
Growth models imply no significant RGR benefit from regulating Vmax.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Outcome
- growth benefit from regulating Vmaxe0
- Direction
- no significante0
- Qualifier
- high nutrient availabilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“Analyses of RGR using growth models imply no significant growth benefit from regulating Vmax, specifically, not from down-regulating it at high nutrient availability”
Claim · model-written summary
Predicted benefits from root:shoot and uptake increases are small under nutrient depletion.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Outcome
- Quantitative benefitse0
- Direction
- quite smalle0
- Qualifier
- nutrient concentrations are significantly depleted by uptakee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“Quantitative benefits of increases in root: shoot ratio and uptake parameters are predicted to be quite small under common conditions wherein nutrient concentrations are significantly depleted by uptake”
Claim · model-written summary
The root:shoot response had the smallest estimated benefit without depletion and largest with depletion.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Outcome
- benefite0
- Qualifier
- non-depleting conditions and the largest benefit under depleting conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“The root: shoot response is estimated to confer the smallest benefit under non-depleting conditions and the largest benefit under depleting conditions”
Claim · model-written summary
Even under depletion, the absolute predicted benefit was small except possibly in heterogeneous soils.
- Taxon
- sunflower plants (Helianthus annuus L.)Helianthus annuust0
- Outcome
- absolute benefite0
- Direction
- smalle0
- Qualifier
- heterogeneous soilse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“sunflower plants (Helianthus annuus L.)”
e0“Even then, the absolute benefit is predicted to be small, possibly excepting the case of heterogeneous soils”
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See all 38 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.