Abstract
The inhibitory effect of ammonium on primary root growth has been well documented; however the underlying physiological and molecular mechanisms are still controversial. To avoid ammonium toxicity to shoot growth, we used a vertical two-layer split plate system, in which the upper layer contained nitrate and the lower layer contained ammonium. In this way, nitrogen status was maintained and only the apical part of the root system was exposed to ammonium. Using a kinematic approach, we show here that 1 mM ammonium reduces primary root growth, decreasing both elemental expansion and cell production. Ammonium inhibits the length of elongation zone and the maximum elemental expansion rate. Ammonium also decreases the apparent length of the meristem as well as the number of dividing cells without affecting cell division rate. Moreover, ammonium reduces the number of root cap cells but appears to affect neither the status of root stem cell niche nor the distal auxin maximum at the quiescent center. Ammonium also inhibits root gravitropism and concomitantly down-regulates the expression of two pivotal auxin transporters, AUX1 and PIN2. Insofar as ammonium inhibits root growth rate in AUX1 and PIN2 loss-of-function mutants almost as strongly as in wild type, we conclude that ammonium inhibits root growth and gravitropism by largely distinct pathways.
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Claims 11
Claim · model-written summary
1 mM ammonium reduced primary root growth in Arabidopsis.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianat0 - Organ / stage
- primary roote0
- Treatment
- 1 mM ammoniume0
- Outcome
- primary root growthe0
- Direction
- reducese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“1 mM ammonium reduces primary root growth”
t0“Arabidopsis thaliana”
Claim · model-written summary
1 mM ammonium decreased both elemental expansion and cell production in the primary root.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- 1 mM ammoniume0
- Outcome
- elemental expansion and cell productione0
- Direction
- decreasinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“1 mM ammonium reduces primary root growth, decreasing both elemental expansion and cell production”
t0“Arabidopsis thaliana”
Claim · model-written summary
Ammonium inhibited the length of the elongation zone and the maximum elemental expansion rate.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Ammoniume0
- Outcome
- length of elongation zone and the maximum elemental expansion ratee0
- Direction
- inhibitse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ammonium inhibits the length of elongation zone and the maximum elemental expansion rate”
t0“Arabidopsis thaliana”
Claim · model-written summary
Ammonium decreased the apparent length of the meristem and the number of dividing cells.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Ammoniume0
- Outcome
- apparent length of the meristem as well as the number of dividing cellse0
- Direction
- decreasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ammonium also decreases the apparent length of the meristem as well as the number of dividing cells”
t0“Arabidopsis thaliana”
Claim · model-written summary
Ammonium did not affect cell division rate.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Ammoniume0
- Outcome
- cell division ratee0
- Direction
- without affectinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ammonium also decreases the apparent length of the meristem as well as the number of dividing cells without affecting cell division rate”
t0“Arabidopsis thaliana”
Claim · model-written summary
Ammonium reduced the number of root cap cells.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- ammoniume0
- Outcome
- number of root cap cellse0
- Direction
- reducese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ammonium reduces the number of root cap cells”
t0“Arabidopsis thaliana”
Claim · model-written summary
Ammonium appeared to affect neither the status of the root stem cell niche nor the distal auxin maximum at the quiescent center.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- ammoniume0
- Outcome
- status of root stem cell niche nor the distal auxin maximum at the quiescent centere0
- Direction
- affect neithere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ammonium reduces the number of root cap cells but appears to affect neither the status of root stem cell niche nor the distal auxin maximum at the quiescent center”
t0“Arabidopsis thaliana”
Claim · model-written summary
Ammonium inhibited root gravitropism.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Ammoniume0
- Outcome
- root gravitropisme0
- Direction
- inhibitse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ammonium also inhibits root gravitropism”
t0“Arabidopsis thaliana”
Claim · model-written summary
Ammonium down-regulated expression of the two auxin transporters AUX1 and PIN2.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Ammoniume0
- Gene
- AUX1 and PIN2e0
- Outcome
- expressione0
- Direction
- down-regulatese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ammonium also inhibits root gravitropism and concomitantly down-regulates the expression of two pivotal auxin transporters, AUX1 and PIN2”
t0“Arabidopsis thaliana”
Claim · model-written summary
Ammonium inhibited root growth rate in AUX1 and PIN2 loss-of-function mutants almost as strongly as in wild type.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Material
- AUX1 and PIN2 loss-of-function mutantse0
- Treatment
- ammoniume0
- Outcome
- root growth ratee0
- Direction
- inhibitse0
- Qualifier
- almost as stronglye0
- Comparator
- wild typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ammonium inhibits root growth rate in AUX1 and PIN2 loss-of-function mutants almost as strongly as in wild type”
t0“Arabidopsis thaliana”
Claim · model-written summary
The authors conclude that ammonium inhibits root growth and gravitropism by largely distinct pathways.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- ammoniume0
- Outcome
- root growth and gravitropisme0
- Qualifier
- largely distinct pathwayse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ammonium inhibits root growth and gravitropism by largely distinct pathways”
t0“Arabidopsis thaliana”
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