Abstract
Ammonium (NH4+) alleviates manganese (Mn) toxicity in various plant species, but the underlying mechanisms are still unclear. In this study, we compared the effects of NH4+ and nitrate (NO3) on rice (Oryza sativa L.) growth, accumulation and distribution of Mn, accumulation of iron (Fe), zinc (Zn) and copper (Cu), root cell wall components and expression of Mn and Fe transporter genes. After rice seedlings were grown in non-pH-buffered nutrient solution for 2 days, the pH of growth medium changed from an initial value of 4.5 to 3.5 and to 5.5 in the presence of NH4+ and in the presence of NO3, respectively. Compared with NO3, ammonium decreased nutrient-solution pH and alleviated Mn toxicity and accumulation in rice under non-pH-buffered conditions. This alleviation disappeared when 5 mM Homo-PIPES pH buffer was added. Regardless of N form, roots, shoots, root cell sap and xylem sap accumulated much lower Mn at pH 3.5 than at pH 5.5, whereas Mn distribution in different leaves and Mn accumulation in root cell walls was affected by neither N form nor pH. Ammonium decreased the expression of the Mn influx transporter gene OsNramp5 in roots under non-pH-buffered conditions, but not under pH-buffered ones. OsNramp5 expression was down-regulated at pH 3.5 compared with pH 5.5. Another efflux Mn transporter gene, OsMTP9, was not regulated by either N form or pH. High pH (5.5) enhanced the expression of the Fe transporter gene OsIRT1 and increased the accumulation of Zn but not Fe or Cu in shoots compared with pH 3.5. Taken together, our results indicate that NH4+ alleviates Mn toxicity and accumulation in rice through the down-regulatory effects of rhizosphere acidification on the Mn influx transporter gene OsNramp5. In addition, the up-regulation of OsIRT1 expression may contribute to the increased Zn uptake by rice at high pH of nutrient solution.
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Claims 14
Claim · model-written summary
Ammonium lowered solution pH to 3.5 versus 5.5 with nitrate.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the pH of growth medium changed from an initial value of 4.5 to 3.5 and to 5.5 in the presence of NH4+ and in the presence of NO3, respectively”
t0“Rice”
Claim · model-written summary
Ammonium alleviated manganese toxicity relative to nitrate without pH buffer.
- Taxon
- rice
Oryza sativae0 - Treatment
- ammoniume0
- Outcome
- Mn toxicitye0
- Direction
- alleviatede0
- Qualifier
- non-pH-buffered conditionse0
- Comparator
- NO3e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with NO3, ammonium decreased nutrient-solution pH and alleviated Mn toxicity and accumulation in rice under non-pH-buffered conditions”
Claim · model-written summary
Ammonium decreased manganese accumulation relative to nitrate without pH buffer.
- Taxon
- riceOryza sativae0
- Treatment
- ammoniume0
- Outcome
- Mn toxicity and accumulatione0
- Direction
- decreasede0
- Qualifier
- non-pH-buffered conditionse0
- Comparator
- NO3e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with NO3, ammonium decreased nutrient-solution pH and alleviated Mn toxicity and accumulation in rice under non-pH-buffered conditions”
Claim · model-written summary
Buffering abolished ammonium-mediated relief of manganese toxicity and accumulation.
- Taxon
- RiceOryza sativat0
- Treatment
- 5 mM Homo-PIPES pH buffere0
- Outcome
- alleviatione0
- Direction
- disappearede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This alleviation disappeared when 5 mM Homo-PIPES pH buffer was added”
t0“Rice”
Claim · model-written summary
Rice roots, shoots, root cell sap and xylem sap accumulated less manganese at pH 3.5 than 5.5.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots, shoots, root cell sap and xylem sap accumulated much lower Mn at pH 3.5 than at pH 5.5”
t0“Rice”
Claim · model-written summary
Leaf manganese distribution was unaffected by nitrogen form or pH.
- Taxon
- RiceOryza sativat0
- Treatment
- N form nor pHe0
- Outcome
- Mn distribution in different leavese0
- Direction
- neithere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Mn distribution in different leaves and Mn accumulation in root cell walls was affected by neither N form nor pH”
t0“Rice”
Claim · model-written summary
Root-cell-wall manganese accumulation was unaffected by nitrogen form or pH.
- Taxon
- RiceOryza sativat0
- Treatment
- N form nor pHe0
- Outcome
- Mn accumulation in root cell wallse0
- Direction
- neithere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Mn distribution in different leaves and Mn accumulation in root cell walls was affected by neither N form nor pH”
t0“Rice”
Claim · model-written summary
Ammonium lowered root OsNramp5 expression without pH buffer but not with buffer.
- Taxon
- RiceOryza sativat0
- Organ / stage
- rootse0
- Treatment
- Ammoniume0
- Gene
- OsNramp5e0
- Outcome
- expression of the Mn influx transporter gene OsNramp5e0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ammonium decreased the expression of the Mn influx transporter gene OsNramp5 in roots under non-pH-buffered conditions, but not under pH-buffered ones”
t0“Rice”
Claim · model-written summary
OsNramp5 expression was lower at pH 3.5 than at pH 5.5.
- Taxon
- RiceOryza sativat0
- Treatment
- pH 3.5e0
- Gene
- OsNramp5e0
- Outcome
- OsNramp5 expressione0
- Direction
- down-regulatede0
- Comparator
- pH 5.5e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“OsNramp5 expression was down-regulated at pH 3.5 compared with pH 5.5”
t0“Rice”
Claim · model-written summary
OsMTP9 was not regulated by nitrogen form or pH.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“OsMTP9, was not regulated by either N form or pH”
t0“Rice”
Claim · model-written summary
Higher pH enhanced OsIRT1 expression.
- Taxon
- RiceOryza sativat0
- Treatment
- High pH (5.5)e0
- Gene
- OsIRT1e0
- Outcome
- expression of the Fe transporter gene OsIRT1e0
- Direction
- enhancede0
- Comparator
- pH 3.5e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“High pH (5.5) enhanced the expression of the Fe transporter gene OsIRT1”
t0“Rice”
e1“High pH (5.5) enhanced the expression of the Fe transporter gene OsIRT1 and increased the accumulation of Zn but not Fe or Cu in shoots compared with pH 3.5”
Claim · model-written summary
Higher pH increased shoot zinc accumulation.
- Taxon
- RiceOryza sativat0
- Organ / stage
- shootse0
- Treatment
- High pH (5.5)e1
- Outcome
- accumulation of Zne0
- Direction
- increasede0
- Comparator
- pH 3.5e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased the accumulation of Zn but not Fe or Cu in shoots compared with pH 3.5”
t0“Rice”
e1“High pH (5.5) enhanced the expression of the Fe transporter gene OsIRT1 and increased the accumulation of Zn but not Fe or Cu in shoots compared with pH 3.5”
Claim · model-written summary
Higher pH did not increase shoot iron accumulation.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased the accumulation of Zn but not Fe or Cu in shoots compared with pH 3.5”
t0“Rice”
e1“High pH (5.5) enhanced the expression of the Fe transporter gene OsIRT1 and increased the accumulation of Zn but not Fe or Cu in shoots compared with pH 3.5”
Claim · model-written summary
Higher pH did not increase shoot copper accumulation.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased the accumulation of Zn but not Fe or Cu in shoots compared with pH 3.5”
t0“Rice”
e1“High pH (5.5) enhanced the expression of the Fe transporter gene OsIRT1 and increased the accumulation of Zn but not Fe or Cu in shoots compared with pH 3.5”
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