Sodium Chloride Enhances Nitrogen Use Efficiency but Reduces Yield Benefits Under Elevated CO<sub>2</sub> in Upland Rice

Sodium Chloride Enhances Nitrogen Use Efficiency but Reduces Yield Benefits Under Elevated CO<sub>2</sub> in Upland Rice

Climate-change-driven elevation of atmospheric CO<sub>2</sub> (e[CO<sub>2</sub>]) disrupts rice physiology by impairing nitrogen use efficiency (NUE) and leaf carbon balance. This study investigated how sodium chloride (NaCl) amendment modulates these processes in upland rice...

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Main Authors: Daniel Amorim Vieira, Mayra Alejandra Toro-Herrera, João Paulo Pennacchi, Marília Mickaele Pinheiro Carvalho, Flavia Barbosa Silva Botelho, Paulo Eduardo Ribeiro Marchiori, João Paulo Rodrigues Alves Delfino Barbosa
Format: Article
Language:English
Published: MDPI AG 2025-05-01
Series:Agronomy
Subjects:
sodium fertilization
climate change
<i>Oryza sativa</i> L.
photorespiration
photosynthetic responses
climate-smart agriculture
Online Access:https://www.mdpi.com/2073-4395/15/5/1212
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Summary:Climate-change-driven elevation of atmospheric CO<sub>2</sub> (e[CO<sub>2</sub>]) disrupts rice physiology by impairing nitrogen use efficiency (NUE) and leaf carbon balance. This study investigated how sodium chloride (NaCl) amendment modulates these processes in upland rice (<i>Oryza sativa</i> L. cv. CMG 2085) under current (400 μmol mol<sup>−1</sup>) and elevated (700 μmol mol<sup>−1</sup>) CO<sub>2</sub> concentrations. Using a randomized block design with factorial treatments (CO<sub>2</sub> × NaCl), we analyzed leaf nutrients, gas exchange, chlorophyll fluorescence, and yield parameters. Our findings revealed that 3 mmol L<sup>−1</sup> NaCl under ambient CO<sub>2</sub> (1) reduced photorespiration by half, (2) increased grain yield, and (3) enhanced leaf area despite lower leaf N content, indicating improved NUE. Conversely, under e[CO<sub>2</sub>], NaCl supplementation decreased rice yield by 15%, demonstrating CO<sub>2</sub>-dependent reversal of sodium benefits. Photosynthetic modeling showed higher Vcmax and J values at ambient CO<sub>2</sub>, while e[CO<sub>2</sub>] increased J/Vcmax, suggesting altered nitrogen allocation to photosynthetic reactions. These results demonstrate that applying low-dose NaCl (3 mmol L<sup>−1</sup>) can optimize carbon and nitrogen economy under current CO<sub>2</sub> concentrations, although its efficacy diminishes under e[CO<sub>2</sub>]. These findings support climate-resilient cultivation strategies for upland rice in tropical and subtropical regions where mild salinity can be used to enhance nitrogen use efficiency and yield under present-day atmospheric conditions.
ISSN:2073-4395

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