当前位置： SCI文献检索 > BMC PLANT BIOLOGY期刊下所有文献 > Depletion of the heaviest stable N isotope is associated with NH4+/NH3 toxicity in NH4+-fed plants.

Depletion of the heaviest stable N isotope is associated with NH4+/NH3 toxicity in NH4+-fed plants.

Abstract：

BACKGROUND:In plants, nitrate (NO3-) nutrition gives rise to a natural N isotopic signature (δ15N), which correlates with the δ15N of the N source. However, little is known about the relationship between the δ15N of the N source and the 14N/15N fractionation in plants under ammonium (NH4+) nutrition. When NH4+ is the major N source, the two forms, NH4+ and NH3, are present in the nutrient solution. There is a 1.025 thermodynamic isotope effect between NH3 (g) and NH4+ (aq) which drives to a different δ15N. Nine plant species with different NH4+-sensitivities were cultured hydroponically with NO3- or NH4+ as the sole N sources, and plant growth and δ15N were determined. Short-term NH4+/NH3 uptake experiments at pH 6.0 and 9.0 (which favours NH3 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 NH4+ and NH3. RESULTS:Several NO3--fed plants were consistently enriched in 15N, whereas plants under NH4+ nutrition were depleted of 15N. It was shown that more sensitive plants to NH4+ toxicity were the most depleted in 15N. In parallel, N-deficient pea and spinach plants fed with 15NH4+ showed an increased level of NH3 uptake at alkaline pH that was related to the 15N depletion of the plant. Tolerant to NH4+ pea plants or sensitive spinach plants showed similar trend on 15N depletion while slight differences in the time kinetics were observed during the initial stages. The use of RbNO3 as control discarded that the differences observed arise from pH detrimental effects. CONCLUSIONS:This article proposes that the negative values of δ15N in NH4+-fed plants are originated from NH3 uptake by plants. Moreover, this depletion of the heavier N isotope is proportional to the NH4+/NH3 toxicity in plants species. Therefore, we hypothesise that the low affinity transport system for NH4+ 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.

journal_name

BMC Plant Biol

journal_title

BMC plant biology

authors

Ariz I,Cruz C,Moran JF,González-Moro MB,García-Olaverri C,González-Murua C,Martins-Loução MA,Aparicio-Tejo PM

doi

10.1186/1471-2229-11-83

subject

Has Abstract

pub_date

2011-05-16 00:00:00

pages

issn

1471-2229

pii

1471-2229-11-83

journal_volume

pub_type

杂志文章

在线工具

Depletion of the heaviest stable N isotope is associated with NH4+/NH3 toxicity in NH4+-fed plants.