Abstract
Concentrations of inorganic cations are often lower in plants supplied with NH4+ as compared with NO3−. To examine whether this is attributable to impaired root uptake of cations or lower internal demand, the rates of uptake and translocation of K, Mg, and Ca were compared in maize plants (Zea mays L.) with different growth-related nutrient demands. Plants were grown in nutrient solution with either 1·0 mol m−3 NO3− or NH4+ and the shoot growth rate per unit weight of roots was modified by varying the temperature of the shoot base (SBT) including the apical shoot meristem. The shoot growth rate per unit weight of roots, which was taken as the parameter for the nutrient demand imposed on the root system, was markedly lower at 12°C than at 24°C SBT. As a consequence of the lower nutrient demand at 12°C SBT, uptake rates of NO3− and NH4+ declined by more than 50% Compared with NO3− supply, NH4+ nutrition depressed the concentrations of K and particularly of Ca in the shoot, both in plants with high and with low nutrient demand. This indicates a control of cation concentration by internal demand rather than by uptake capacity of the roots. Translocation rates of K, Mg and Ca in the xylem exudate were lower in NH4+- than in NO3−-fed plants. Net accumulation rates of Ca in the shoot were also decreased, whereas net accumulation rates of K in the shoot were even higher in NH4+-fed plants. It is concluded that reduced cation concentrations in the xylem sap of plants supplied with NH4+ are due to the lower demand of cations for charge balance. The lower K translocation to the shoot is compensated by reduced retranslocation to the roots. For Ca, in contrast, decreased translocation rates in NH4+-fed plants result in lower shoot concentration.
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Claims 11
Claim · model-written summary
Shoot growth per root weight was lower at 12°C than 24°C.
- Treatment
- 12°Ce0
- Outcome
- shoot growth rate per unit weight of rootse0
- Direction
- lowere0
- Comparator
- 24°C SBTe0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The shoot growth rate per unit weight of roots, which was taken as the parameter for the nutrient demand imposed on the root system, was markedly lower at 12°C than at 24°C SBT”
t0“Maize”
Claim · model-written summary
Lower shoot-base temperature reduced nitrate uptake by more than 50%.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“As a consequence of the lower nutrient demand at 12°C SBT, uptake rates of NO3− and NH4+ declined by more than 50%”
t0“Maize”
Claim · model-written summary
Lower shoot-base temperature reduced ammonium uptake by more than 50%.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“As a consequence of the lower nutrient demand at 12°C SBT, uptake rates of NO3− and NH4+ declined by more than 50%”
t0“Maize”
Claim · model-written summary
Ammonium nutrition reduced shoot potassium concentration versus nitrate at both nutrient demands.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with NO3− supply, NH4+ nutrition depressed the concentrations of K and particularly of Ca in the shoot, both in plants with high and with low nutrient demand”
t0“Maize”
Claim · model-written summary
Ammonium nutrition particularly reduced shoot calcium concentration versus nitrate.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with NO3− supply, NH4+ nutrition depressed the concentrations of K and particularly of Ca in the shoot, both in plants with high and with low nutrient demand”
t0“Maize”
Claim · model-written summary
Ammonium-fed plants had lower xylem translocation rates of K, Mg and Ca than nitrate-fed plants.
- Treatment
- NH4+-e0
- Outcome
- Translocation rates of K, Mg and Cae0
- Direction
- lowere0
- Comparator
- NO3−-fed plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Translocation rates of K, Mg and Ca in the xylem exudate were lower in NH4+- than in NO3−-fed plants”
t0“Maize”
Claim · model-written summary
Ammonium-fed plants had decreased calcium accumulation in shoots.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Net accumulation rates of Ca in the shoot were also decreased, whereas net accumulation rates of K in the shoot were even higher in NH4+-fed plants”
t0“Maize”
Claim · model-written summary
Ammonium-fed plants had higher potassium accumulation in shoots.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Net accumulation rates of Ca in the shoot were also decreased, whereas net accumulation rates of K in the shoot were even higher in NH4+-fed plants”
t0“Maize”
Claim · model-written summary
Authors attribute lower cation concentration in ammonium-fed xylem sap to lower charge-balance demand.
- Treatment
- NH4+e0
- Outcome
- reduced cation concentrations in the xylem sape0
- Qualifier
- lower demand of cations for charge balancee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reduced cation concentrations in the xylem sap of plants supplied with NH4+ are due to the lower demand of cations for charge balance”
t0“Maize”
Claim · model-written summary
Reduced retranslocation to roots compensates lower shoot potassium translocation.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The lower K translocation to the shoot is compensated by reduced retranslocation to the roots”
t0“Maize”
Claim · model-written summary
Authors infer lower calcium translocation causes lower shoot calcium concentration under ammonium nutrition.
- Treatment
- NH4+-fed plantse0
- Outcome
- lower shoot concentratione0
- Qualifier
- decreased translocation ratese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For Ca, in contrast, decreased translocation rates in NH4+-fed plants result in lower shoot concentration”
t0“Maize”
The same questions in other papers
ammonium · nutrient: content · Zea mays (maize)Positive and negative results
1 paper in the same direction as this paper · 2 in the opposite direction
- positive
- positive
- no effect
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.