Abstract
Increasing the nitrate (N) concentration in the rooting substrate above deficiency decreased stomatal conductance and leaf growth rate compared with sufficient N in maize seedlings (Zea mays L.) growing in drying substrate. Novel effects were detected when N in the non-deficient range was supplied directly to the xylem of detached shoots: concentrations above 2.0 mol m-3 KNO3 reduced transpiration, and concentrations above 12 mol m-3 KNO3 reduced leaf growth rate. Evidence is provided that the novel effects of N on transpiration and growth were mediated by pH-based ABA redistribution. ABA at 0.05 mol m-3, whilst ineffective alone, sensitized leaf growth to increases in KNO3 concentration (from 3.0 mol m-3), and the capacity of higher concentrations of ABA to reduce growth was enhanced by KNO3. Transpiration was sensitively reduced by KNO3, ABA, or buffers adjusted to pH 6.7-7.0 (compared with buffers adjusted to pH 5.0) alone. Nevertheless, a synergistic effect of KNO3 and either ABA or buffers adjusted to pH 6.7-7.0 was observed. Buffers of pH 5.6 supplied to detached shoots alleviated the depression of transpiration caused by 12 mol m-3 KNO3. Buffers adjusted to pH 6.7 increased the sensitivity of growth to KNO3. Xylem sap extracted from intact seedlings growing in drying soil exhibited an initial increase in N concentration, followed by a decrease at progressively lower soil water potentials. The importance for novel N signalling above deficiency is discussed with reference to the generality of fluctuations in soil and xylem N concentration within this range.
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Claims 15
Claim · model-written summary
Above-deficiency nitrate decreased stomatal conductance in maize growing in drying substrate.
- Treatment
- Increasing the nitrate (N) concentration in the rooting substrate above deficiencye0
- Outcome
- stomatal conductancee0
- Direction
- decreasede0
- Comparator
- sufficient Ne0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increasing the nitrate (N) concentration in the rooting substrate above deficiency decreased stomatal conductance and leaf growth rate compared with sufficient N in maize seedlings (Zea mays L.) growing in drying substrate.”
Claim · model-written summary
Above-deficiency nitrate decreased maize leaf growth rate in drying substrate.
- Treatment
- Increasing the nitrate (N) concentration in the rooting substrate above deficiencye0
- Outcome
- leaf growth ratee0
- Direction
- decreasede0
- Comparator
- sufficient Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increasing the nitrate (N) concentration in the rooting substrate above deficiency decreased stomatal conductance and leaf growth rate compared with sufficient N in maize seedlings (Zea mays L.) growing in drying substrate.”
Claim · model-written summary
Xylem KNO3 above 2.0 mol m-3 reduced transpiration in detached maize shoots.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“concentrations above 2.0 mol m-3 KNO3 reduced transpiration”
t0“maize”
Claim · model-written summary
Xylem KNO3 above 12 mol m-3 reduced maize leaf growth rate.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“concentrations above 12 mol m-3 KNO3 reduced leaf growth rate”
t0“maize”
Claim · model-written summary
Nitrate effects on transpiration and growth were attributed to pH-based ABA redistribution.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the novel effects of N on transpiration and growth were mediated by pH-based ABA redistribution.”
t0“maize”
Claim · model-written summary
ABA at 0.05 mol m-3 sensitized maize leaf growth to KNO3 increases from 3.0 mol m-3.
- Treatment
- ABA at 0.05 mol m-3e0
- Outcome
- leaf growthe0
- Direction
- sensitizede0
- Comparator
- ineffective alonee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA at 0.05 mol m-3, whilst ineffective alone, sensitized leaf growth to increases in KNO3 concentration (from 3.0 mol m-3)”
t0“maize”
Claim · model-written summary
KNO3 enhanced the growth-reducing capacity of higher ABA concentrations.
- Treatment
- KNO3e0
- Outcome
- capacity of higher concentrations of ABA to reduce growthe0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the capacity of higher concentrations of ABA to reduce growth was enhanced by KNO3.”
t0“maize”
Claim · model-written summary
KNO3 reduced maize transpiration.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transpiration was sensitively reduced by KNO3, ABA, or buffers adjusted to pH 6.7-7.0 (compared with buffers adjusted to pH 5.0) alone.”
t0“maize”
Claim · model-written summary
ABA reduced maize transpiration.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transpiration was sensitively reduced by KNO3, ABA, or buffers adjusted to pH 6.7-7.0 (compared with buffers adjusted to pH 5.0) alone.”
t0“maize”
Claim · model-written summary
Buffers at pH 6.7-7.0 reduced transpiration relative to pH 5.0.
- Treatment
- buffers adjusted to pH 6.7-7.0e0
- Outcome
- Transpiratione0
- Direction
- reducede0
- Comparator
- buffers adjusted to pH 5.0e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transpiration was sensitively reduced by KNO3, ABA, or buffers adjusted to pH 6.7-7.0 (compared with buffers adjusted to pH 5.0) alone.”
t0“maize”
Claim · model-written summary
KNO3 and ABA synergistically reduced maize transpiration.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a synergistic effect of KNO3 and either ABA or buffers adjusted to pH 6.7-7.0 was observed.”
t0“maize”
Claim · model-written summary
KNO3 and high-pH buffer showed a synergistic effect on transpiration.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a synergistic effect of KNO3 and either ABA or buffers adjusted to pH 6.7-7.0 was observed.”
t0“maize”
Claim · model-written summary
pH 5.6 buffer alleviated transpiration depression from 12 mol m-3 KNO3.
- Treatment
- Buffers of pH 5.6e0
- Outcome
- depression of transpiratione0
- Direction
- alleviatede0
- Comparator
- 12 mol m-3 KNO3e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Buffers of pH 5.6 supplied to detached shoots alleviated the depression of transpiration caused by 12 mol m-3 KNO3.”
t0“maize”
Claim · model-written summary
pH 6.7 buffer increased growth sensitivity to KNO3.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Buffers adjusted to pH 6.7 increased the sensitivity of growth to KNO3.”
t0“maize”
Claim · model-written summary
Xylem sap nitrogen initially increased during soil drying, then decreased at lower water potentials.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Xylem sap extracted from intact seedlings growing in drying soil exhibited an initial increase in N concentration, followed by a decrease at progressively lower soil water potentials.”
t0“maize”
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