Depletion of the heaviest stable N isotope is associated with NH<sub>4</sub><sup>+</sup>/NH<sub>3 </sub>toxicity in NH<sub>4</sub><sup>+</sup>-fed plants
<p>Abstract</p> <p>Background</p> <p>In plants, nitrate (NO<sub>3</sub><sup>-</sup>) nutrition gives rise to a natural N isotopic signature (δ<sup>15</sup>N), which correlates with the δ<sup>15</sup>N of the N source. Howe...
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| Format: | Article |
| Language: | English |
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BMC
2011-05-01
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| Series: | BMC Plant Biology |
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| Online Access: | http://www.biomedcentral.com/1471-2229/11/83 |
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| author | Martins-Loução Maria A González-Murua Carmen García-Olaverri Carmen González-Moro María B Moran Jose F Cruz Cristina Ariz Idoia Aparicio-Tejo Pedro M |
| author_facet | Martins-Loução Maria A González-Murua Carmen García-Olaverri Carmen González-Moro María B Moran Jose F Cruz Cristina Ariz Idoia Aparicio-Tejo Pedro M |
| author_sort | Martins-Loução Maria A |
| collection | DOAJ |
| description | <p>Abstract</p> <p>Background</p> <p>In plants, nitrate (NO<sub>3</sub><sup>-</sup>) nutrition gives rise to a natural N isotopic signature (δ<sup>15</sup>N), which correlates with the δ<sup>15</sup>N of the N source. However, little is known about the relationship between the δ<sup>15</sup>N of the N source and the <sup>14</sup>N/<sup>15</sup>N fractionation in plants under ammonium (NH<sub>4</sub><sup>+</sup>) nutrition. When NH<sub>4</sub><sup>+ </sup>is the major N source, the two forms, NH<sub>4</sub><sup>+ </sup>and NH<sub>3</sub>, are present in the nutrient solution. There is a 1.025 thermodynamic isotope effect between NH<sub>3 </sub>(g) and NH<sub>4</sub><sup>+ </sup>(aq) which drives to a different δ<sup>15</sup>N. Nine plant species with different NH<sub>4</sub><sup>+</sup>-sensitivities were cultured hydroponically with NO<sub>3</sub><sup>- </sup>or NH<sub>4</sub><sup>+ </sup>as the sole N sources, and plant growth and δ<sup>15</sup>N were determined. Short-term NH<sub>4</sub><sup>+</sup>/NH<sub>3 </sub>uptake experiments at pH 6.0 and 9.0 (which favours NH<sub>3 </sub>form) were carried out in order to support and substantiate our hypothesis. N source fractionation throughout the whole plant was interpreted on the basis of the relative transport of NH<sub>4</sub><sup>+ </sup>and NH<sub>3</sub>.</p> <p>Results</p> <p>Several NO<sub>3</sub><sup>-</sup>-fed plants were consistently enriched in <sup>15</sup>N, whereas plants under NH<sub>4</sub><sup>+ </sup>nutrition were depleted of <sup>15</sup>N. It was shown that more sensitive plants to NH<sub>4</sub><sup>+ </sup>toxicity were the most depleted in <sup>15</sup>N. In parallel, N-deficient pea and spinach plants fed with <sup>15</sup>NH<sub>4</sub><sup>+ </sup>showed an increased level of NH<sub>3 </sub>uptake at alkaline pH that was related to the <sup>15</sup>N depletion of the plant. Tolerant to NH<sub>4</sub><sup>+ </sup>pea plants or sensitive spinach plants showed similar trend on <sup>15</sup>N depletion while slight differences in the time kinetics were observed during the initial stages. The use of RbNO<sub>3 </sub>as control discarded that the differences observed arise from pH detrimental effects.</p> <p>Conclusions</p> <p>This article proposes that the negative values of δ<sup>15</sup>N in NH<sub>4</sub><sup>+</sup>-fed plants are originated from NH<sub>3 </sub>uptake by plants. Moreover, this depletion of the heavier N isotope is proportional to the NH<sub>4</sub><sup>+</sup>/NH<sub>3 </sub>toxicity in plants species. Therefore, we hypothesise that the low affinity transport system for NH<sub>4</sub><sup>+ </sup>may have two components: one that transports N in the molecular form and is associated with fractionation and another that transports N in the ionic form and is not associated with fractionation.</p> |
| first_indexed | 2024-04-13T11:09:39Z |
| format | Article |
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| institution | Directory Open Access Journal |
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| language | English |
| last_indexed | 2024-04-13T11:09:39Z |
| publishDate | 2011-05-01 |
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| series | BMC Plant Biology |
| spelling | doaj.art-35bdef0208564abe9559ce5f129be6f42022-12-22T02:49:10ZengBMCBMC Plant Biology1471-22292011-05-011118310.1186/1471-2229-11-83Depletion of the heaviest stable N isotope is associated with NH<sub>4</sub><sup>+</sup>/NH<sub>3 </sub>toxicity in NH<sub>4</sub><sup>+</sup>-fed plantsMartins-Loução Maria AGonzález-Murua CarmenGarcía-Olaverri CarmenGonzález-Moro María BMoran Jose FCruz CristinaAriz IdoiaAparicio-Tejo Pedro M<p>Abstract</p> <p>Background</p> <p>In plants, nitrate (NO<sub>3</sub><sup>-</sup>) nutrition gives rise to a natural N isotopic signature (δ<sup>15</sup>N), which correlates with the δ<sup>15</sup>N of the N source. However, little is known about the relationship between the δ<sup>15</sup>N of the N source and the <sup>14</sup>N/<sup>15</sup>N fractionation in plants under ammonium (NH<sub>4</sub><sup>+</sup>) nutrition. When NH<sub>4</sub><sup>+ </sup>is the major N source, the two forms, NH<sub>4</sub><sup>+ </sup>and NH<sub>3</sub>, are present in the nutrient solution. There is a 1.025 thermodynamic isotope effect between NH<sub>3 </sub>(g) and NH<sub>4</sub><sup>+ </sup>(aq) which drives to a different δ<sup>15</sup>N. Nine plant species with different NH<sub>4</sub><sup>+</sup>-sensitivities were cultured hydroponically with NO<sub>3</sub><sup>- </sup>or NH<sub>4</sub><sup>+ </sup>as the sole N sources, and plant growth and δ<sup>15</sup>N were determined. Short-term NH<sub>4</sub><sup>+</sup>/NH<sub>3 </sub>uptake experiments at pH 6.0 and 9.0 (which favours NH<sub>3 </sub>form) were carried out in order to support and substantiate our hypothesis. N source fractionation throughout the whole plant was interpreted on the basis of the relative transport of NH<sub>4</sub><sup>+ </sup>and NH<sub>3</sub>.</p> <p>Results</p> <p>Several NO<sub>3</sub><sup>-</sup>-fed plants were consistently enriched in <sup>15</sup>N, whereas plants under NH<sub>4</sub><sup>+ </sup>nutrition were depleted of <sup>15</sup>N. It was shown that more sensitive plants to NH<sub>4</sub><sup>+ </sup>toxicity were the most depleted in <sup>15</sup>N. In parallel, N-deficient pea and spinach plants fed with <sup>15</sup>NH<sub>4</sub><sup>+ </sup>showed an increased level of NH<sub>3 </sub>uptake at alkaline pH that was related to the <sup>15</sup>N depletion of the plant. Tolerant to NH<sub>4</sub><sup>+ </sup>pea plants or sensitive spinach plants showed similar trend on <sup>15</sup>N depletion while slight differences in the time kinetics were observed during the initial stages. The use of RbNO<sub>3 </sub>as control discarded that the differences observed arise from pH detrimental effects.</p> <p>Conclusions</p> <p>This article proposes that the negative values of δ<sup>15</sup>N in NH<sub>4</sub><sup>+</sup>-fed plants are originated from NH<sub>3 </sub>uptake by plants. Moreover, this depletion of the heavier N isotope is proportional to the NH<sub>4</sub><sup>+</sup>/NH<sub>3 </sub>toxicity in plants species. Therefore, we hypothesise that the low affinity transport system for NH<sub>4</sub><sup>+ </sup>may have two components: one that transports N in the molecular form and is associated with fractionation and another that transports N in the ionic form and is not associated with fractionation.</p>http://www.biomedcentral.com/1471-2229/11/83Low affinity ammonium transportersNitrogen isotopic signatureAmmonium/ammoniaAmmonium dissociation isotope factorammonia uptake |
| spellingShingle | Martins-Loução Maria A González-Murua Carmen García-Olaverri Carmen González-Moro María B Moran Jose F Cruz Cristina Ariz Idoia Aparicio-Tejo Pedro M Depletion of the heaviest stable N isotope is associated with NH<sub>4</sub><sup>+</sup>/NH<sub>3 </sub>toxicity in NH<sub>4</sub><sup>+</sup>-fed plants BMC Plant Biology Low affinity ammonium transporters Nitrogen isotopic signature Ammonium/ammonia Ammonium dissociation isotope factor ammonia uptake |
| title | Depletion of the heaviest stable N isotope is associated with NH<sub>4</sub><sup>+</sup>/NH<sub>3 </sub>toxicity in NH<sub>4</sub><sup>+</sup>-fed plants |
| title_full | Depletion of the heaviest stable N isotope is associated with NH<sub>4</sub><sup>+</sup>/NH<sub>3 </sub>toxicity in NH<sub>4</sub><sup>+</sup>-fed plants |
| title_fullStr | Depletion of the heaviest stable N isotope is associated with NH<sub>4</sub><sup>+</sup>/NH<sub>3 </sub>toxicity in NH<sub>4</sub><sup>+</sup>-fed plants |
| title_full_unstemmed | Depletion of the heaviest stable N isotope is associated with NH<sub>4</sub><sup>+</sup>/NH<sub>3 </sub>toxicity in NH<sub>4</sub><sup>+</sup>-fed plants |
| title_short | Depletion of the heaviest stable N isotope is associated with NH<sub>4</sub><sup>+</sup>/NH<sub>3 </sub>toxicity in NH<sub>4</sub><sup>+</sup>-fed plants |
| title_sort | depletion of the heaviest stable n isotope is associated with nh sub 4 sub sup sup nh sub 3 sub toxicity in nh sub 4 sub sup sup fed plants |
| topic | Low affinity ammonium transporters Nitrogen isotopic signature Ammonium/ammonia Ammonium dissociation isotope factor ammonia uptake |
| url | http://www.biomedcentral.com/1471-2229/11/83 |
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